Nearly a century later, Russian planners still view Deep Battle as a foundational concept. Yet the war in Ukraine has exposed the performance gap between theory and practice.

Deep Battle in Russian Military Thought

Deep Battle was designed as a holistic operational approach: massed firepower, rapid penetration, and exploitation by mobile formations. It required tight coordination, robust logistics, and the ability to sustain momentum across multiple echelons. Soviet forces demonstrated aspects of this during World War II, and the concept remained embedded in Russian doctrine long after.

Modern Russian operations—at least on paper—still aspire to this model. Analysts note that Russian commanders have attempted to regain maneuver by applying Deep Battle principles, seeking rapid breakthroughs and deep strikes to disorganize Ukrainian defenses. However, the conditions required for successful Deep Battle are far more demanding than the theory suggests.

Why Deep Battle Has Struggled in Ukraine

Several factors have undermined Russia’s ability to execute Deep Battle effectively. Logistical fragility has plagued Russian operations, as sustaining supply to fast-moving units proved difficult; forces entering Ukraine in 2022 quickly outran their logistics, leading to stalled advances and exposed columns. Scholars argue that this logistical weakness fundamentally compromised Russia’s ability to maintain operational tempo. Additionally, Ukrainian resilience and adaptability have presented unexpected challenges. Ukrainian forces have been far more agile and technologically integrated than Russian planners anticipated, employing precision fires, dispersed command structures, and Western intelligence support to blunt Russian attempts at operational shock and interrupting supply lines and replacement equipment. Their use of drone and counter-drone technology exemplifies adaptive learning that has already been noted and copied by other state militaries.

Russia’s attempts at Deep Battle are further hindered by insufficient force quality and added maneuver complexity, as the doctrine relies on well-trained, coordinated echelons. Russia’s reliance on mobilized troops, fragmented command structures, and heavy attrition has made synchronized deep operations difficult to sustain. The loss of air superiority has limited Russia’s ability to shape the battlefield making the battlefield more complex. As intended by doctrine, Soviet Deep Battle assumes overwhelming air support to suppress enemy depth, but contested airspace in Ukraine has prevented this crucial element.

Where Russia Has Adapted

Despite these challenges, Russia has applied Deep Battle concepts in modified ways. In adapting the principles of Deep Battle to modern conflict, Russia has focused on targeting Ukrainian infrastructure with long-range strikes. This campaign has prioritized attacks on energy systems and logistics nodes, aiming to disrupt Ukrainian depth and sustain pressure even without accompanying maneuver. By striking critical assets far from the front lines, Russia attempts to weaken Ukraine’s ability to resist and maintain its war effort.

Rather than achieving rapid breakthroughs as originally envisioned by Deep Battle doctrine, Russia has shifted to a strategy of incremental, attritional “deepening.” This approach relies on massed artillery and slow, grinding advances to steadily erode Ukrainian defenses. The result is a war of attrition where progress is measured in small territorial gains instead of dramatic operational shifts, demonstrating an adaptation of Deep Battle’s objectives without its characteristic momentum.

In addition to these methods, Russian military planners and observers continue to pursue efforts to reconstitute maneuver forces. Despite ongoing challenges, such as limited operational success, attempts are being made to rebuild the capacity for operational-level breakthroughs. These efforts underscore a persistent desire within Russian strategy to reclaim the maneuver warfare and deep operational reach that are central to Deep Battle theory, even as practical limitations remain.

The Role of Nuclear Weapons in Deep Battle

Vladimir Putin has repeatedly issued veiled or explicit warnings regarding the potential for Russian nuclear first use concerning the possibility of Russian nuclear first use in response to perceived unacceptable threats. This stance is further reflected in Russian military exercises, which have frequently included simulated launches with tactical nuclear weapons systems. However, it is important to note that some Soviet assessments during the Cold War adopted a realistically pessimistic outlook on the conduct of military operations in a nuclear environment, recognizing the immense challenges such conditions would impose.

Taken together, these perspectives highlight the duality in Russian strategic thinking: while nuclear signaling and preparation remain integral to Russia’s military posture, there is also an awareness—rooted in historical experience—of the profound difficulties associated with waging war in a nuclear-affected battlespace.

Implications for the Future of the War

Understanding Russia’s attachment to Deep Battle helps explain both its ambitions and its limitations. Russia will continue seeking opportunities for operational breakthroughs, even if conditions rarely allow them. The concept remains deeply embedded in Russian military culture. At the same time, Ukraine’s strategy of disrupting Russian logistics and command nodes directly targets the prerequisites of Deep Battle, making it harder for Russia to generate momentum. If Russia can rebuild its logistics, improve training, and integrate drones and electronic warfare more effectively, it may regain the ability to conduct deeper operations—but this remains uncertain. The war is likely to remain attritional because neither side currently possesses the combination of mass, mobility, and air dominance required for true Deep Battle.

Conclusion

Deep Battle remains a conceptual framework and historical marker for understanding Russian military behavior. But the war in Ukraine has shown that doctrine alone cannot compensate for structural weaknesses, resilient opposition, and the realities of modern precision warfare. Russia’s struggle to translate Deep Battle theory into battlefield success underscores the widening gap between its strategic aspirations and its operational capabilities.

NOTE: The author provides a grateful acknowledgment that is made to David Glantz and the late Dr. Jacob Kipp for the author’s appreciation of this topic. None bear any responsibility for arguments herein.

Stephen J. Cimbala is Distinguished Professor of Political Science at Penn State Brandywine and the author of numerous works on nuclear deterrence, arms control, and military strategy.  He is a senior fellow at NIDS and a recent contributor to the Routledge Handbook of Soviet and Russian Military Studies edited by Dr. Alexander Hill (Routledge: 2025).

The Russian View of Deep Battle: Implications for the War in Ukraine was originally published on Global Security Review.

The United Kingdom’s Defense Issues

The United Kingdom’s military spent several decades downsizing its military. Still, the UK took part in major conflicts in Afghanistan, Iraq, Libya, and Syria, showing that Britain continues to have some force projection capability.

Nevertheless, British Ministry of Defence (MoD) data shows recruitment shortfalls over the past five years. Recent data published by the UK Defence Journal show the biggest recruitment shortfalls are found in the army, where manpower gaps in land forces are most pronounced.

A major factor in recruiting failure was a several-year attempt to draw down spending, that included the army’s closure of half of its recruiting offices, according to the Royal United Services Institute (RUSI). A lack of recruiting offices only erodes the interaction between recruiters and the community. This lack of interaction dissuades civilians, who may not fully understand the benefits of military service, from joining.

Furthermore, an aging population, a rise in health risks, and an extremely long pipeline from recruitment to basic training can dissuade young men and women from choosing service. While Britain’s Air Force and elite Royal Marines remain formidable, further emphasis on naval power and regrowing the land forces is much needed.

Canada’s Rearmament Crisis

The Canadian Armed Forces are currently facing a readiness crisis. According to an internal overview by the Department of National Defence, only 58 percent of the military is ready to handle any situation. Canada’s lack of readiness is increasingly causing concern among the general public. War in Eastern Europe and Africa and brewing conflicts in Asia show the need for North Atlantic Treaty Organization (NATO) member-states to bolster each region. Canada’s military is unready to face a crisis.

A major challenge is stagnation in the Air Force and Navy, where much equipment is neglected and degraded. Because logistics win wars, Canada needs to recruit and train support personnel such as technicians, maintenance, supply, and communications personnel.

Australia’s Defense Issues

Australia, a rising regional power in the Indo-Pacific, also faces challenges for the Australian Defence Forces. Being a member of the trilateral security partnership between Australia, the UK, and the US (AUKUS), Australia is currently awaiting the construction and transfer of three to five Virginia-class submarines from the United States, which may not come in time for Pillar II of the AUKUS agreement, due to stagnant American naval production rates.

Only 80 percent of the 69,000 recruits needed to enhance the Australian Defence Forces have either signed up or met recruiting requirements. Simultaneously, younger Australians feel they have better economic and social opportunities in the private sector than in the military, drawing potential recruits away.

Continuously growing defense spending over several decades will be critical in maintaining readiness. Decades of neglecting defense forced the Australian military into a position where it must catch up to other mid-sized powers like Japan and South Korea. Furthermore, as the Australian Strategic Policy Institute noted, confidence in the military remains low. Thus, efforts to change this view are needed in the information sphere if public institutions are to effectively remilitarize, in lieu of rising threats.

Recommendations for Each Country

The United Kingdom, Canada, and Australia face major recruitment and militarization woes. However, steps can be taken for all three countries to push towards modernization and expansion. This is particularly important if these Anglo nations are to remain a close alliance.

British recruitment woes correlate with the lack of recruitment offices. The British Ministry of Defence must grow and lobby for more offices and events where promising youth can learn and gather information about military service. Furthermore, efforts are needed in the more neglected Royal Navy and Army.

The British have an opportunity to take a leadership position on the continent. Growing the British military will also support defense exports and further enhance and expand the military—albeit with an effort to increase the MOD’s budget.

Canada’s efforts must include broader government support for the military as Canadians question the credibility of a government that drew down the military to ineffectiveness. The Canadian Defence Ministry can also take lessons from NATO partners, such as Poland, Romania, Finland, and others, who are modernizing successfully.

Australia’s expansion of the military must take a two-pronged approach. First, show potential recruits the benefits of military service. Second, the government must instill a sense of patriotism and respect for the Armed Forces. The government can focus on brewing threats in the Indo-Pacific, which will eventually reach Australia, while explaining the benefits of military service.

The Commonwealth countries of the United Kingdom, Australia, and Canada all have capable yet stagnant militaries. Addressing problems with recruitment, logistics, and maintenance can reduce stagnation and help restore these nations’ military strength. As close allies of the United States, their success matters.

Julian McBride is a former US Marine. He is a forensic anthropologist and independent journalist.

Commonwealth Defense and Recruitment Hurdles was originally published on Global Security Review.

Total NATO military expenditures for 2024 are estimated at $1.474.4 trillion. As Russia grows increasingly assertive, many on both sides of the Atlantic are wondering how NATO member-states will step up and contribute to the continent’s defense.

To withstand a Russian attack, NATO must plan for between 35 and 50 extra brigades of 3,000–7,000 troops each—adding 105,000–350,000 soldiers. Germany must contribute 3–5 extra brigades or 20,000–30,000 combat troops.

Protection from air attacks is a major German and Eastern European vulnerability. Former German Defense Minister and current President of the European Commission Ursula van der Leyen recently emphasized the need for Germany, under its new defense plans, to quadruple its air defenses. That includes Patriot missile batteries and shorter-range systems to protect bases, ports, and railway transportation systems.

Should Russia attack NATO, hundreds of thousands of troops, together with tanks, equipment, and ammunitions, will have to make their way to the eastern front through Germany. Preparations for war with Russia indicate that Poland, the Baltics, and other Eastern NATO allies are primary targets, but so is Germany. During the Cold War, Germany had 36 Patriot missile air defense units. The count is down to nine—after donating three to Ukraine. Berlin just ordered four Patriot missile units at a cost of 1.35 billion euros.

The United States spends about 3.5 percent of its gross domestic product (GDP) on defense, but the Congressional Budget Office projects that will fall to 2.5 percent by 2034. NATO member-states recently issued a joint communique that said, “We reaffirm that, in many cases, expenditure beyond 2 percent of GDP will be needed in order to remedy existing shortfalls and meet the requirements across all domains arising from a more contested security order.”

The Baltic states are adamant about the need for increased defense spending. Tuuli Duneton, Estonia’s Undersecretary for Defense Policy, praised the 23 NATO member-states who now meet the 2 percent spending target. She suggested raising the spending goal to 2.5 to 3 percent.

Pointing to NATO’s “capability gaps,” Lithuanian Defense Minister Laurynas Kasčiūna stated, “We’ll start to talk at least about 2.5 percent as a floor,” pointing to NATO’s “capability gaps.” He added, “When we analyze what the countries need to develop soon, for a decade maybe, it’s not even 2.5 percent. It’s not even 3 percent. It should be more if you want more air defense systems, if you want more long-range strike capabilities.”

NATO plans focus on logistics, troop movement, and cyber defenses in preparation for conflict with Russia. After NATO’s plans for the biggest defense upgrade in three decades were agreed upon last year, now is the moment of truth: the minimum defense requirements to meet these plans were sent to national governments, highlighting significant shortfalls in air defenses, long-range missiles, troop numbers, ammunition, logistics, and secure digital communications.

Fixing these shortfalls requires billions of euros in investment. By autumn 2025, NATO aims to set binding targets for members to ensure Europe’s defense. Achieving these targets may be difficult due to budgetary constraints and differing views on NATO’s stance towards Russia.

NATO’s effort to navigate a moment of clear and present danger is made more difficult by the Herculean task of rearming. Deep industrial reconstitution and technological evolution are both needed and taking place across all value chains in all defense tech investments, including space, cyber, drones, and the role of artificial intelligence on the battlefield. Despite its current state of political uncertainty, change-adverse politicians and populations must be convinced of the need for refocusing on defense.

Europe must face a Kulturkampf in which Europeans overcome the three decades of cognitive denial about war in Europe. The biggest obstacle to the above efforts is likely to come from populations that are accustomed to generous welfare programs at the expense of defense preparations. Europe cannot tax its way out of its current problem. European taxes are already the highest in the world.

Compelling communication strategies are essential to justify the increased defense budgets. Officials need to emphasize the pan-European necessity for national and regional security. The twin brother of blood and treasure returned from a long hiatus. Making the argument to citizens becomes an even tougher sell if conscription across Europe is required to mobilize hundreds of thousands of troops to fight.

Asking ordinary citizens in Western or Southern Europe whether they are willing to die for Ukraine or Lithuania or even Poland will likely draw a negative response. Not all European populations seem willing, able, and ready to fight as nation-states united under the concept of pan-European patriotic defense. Those now leading the effort de guerre are found among Poles, Balts, and, in no small part, the newly energized Nordic countries.

In short, if Europe wishes to survive, it must adapt, deter, and defend itself now. Waiting will only add more blood and treasure to the bill that must be paid.

Christophe Bosquillon is a Senior Fellow at the National Institute for Deterrence Studies. He has over 30 years of international experience in general management, foreign direct investment, and private equity and fund management across various industries in Europe and the Pacific Basin. Views expressed in this article are the author’s own.

NATO’s Defense Math Does Not Add Up was originally published on Global Security Review.

The democratic transition in Sudan was halted in October 2021 when General Abdel Fattah al-Burhane conducted a military coup. Ongoing confrontations between the Rapid Support Forces and the Sudanese Armed Forces keep the country in perpetual instability. They have also drawn civilians into the bloodshed.

Guinean president Alpha Condé was ousted in a September 2021 coup, and his successors pledged to bring in a civilian government by 2024. This has yet to happen.

Two coups occurred in Mali within a short period of time. The first coup occurred in August 2020, and the second one took place in May 2021. The military government promises to restore civilian control. It has not.

Shortly after Gabon’s President, Ali Bongo Ondimba, was re-elected in August 2023, a military coup d’état removed him from power, casting doubt on the legitimacy of the election. Ondimba is but one more example of this trend.

Leaders of these coups frequently use security and governance failures as justification for the actions taken. In reality, they tend to worsen stability and undermine democratic processes. The frequent occurrence of military takeovers in such politically unstable countries adds complexity to diplomatic endeavours and presents substantial obstacles to regional development, stability, and security, including the proliferation of insurgencies and terrorist organizations.

However, a notable trend among these nations in recent years is the steady rise of Russian presence and influence. Over the past few months, there were significant events involving Russian armed groups in Africa, which highlighted Moscow’s growing influence and strategic interests in the region. Russian actions have far-reaching consequences for countering Western influence, especially from the European Union and the United States.

Russia is already strengthening its military ties with several African nations, including those that saw political upheaval in recent years. In May, Russia began implementing a military cooperation agreement with São Tomé and Príncipe, which involves joint exercises, education, training, and logistics.

Guinea-Bissau further strengthened connections with Russia, as President Umaro Sissoco Embalo engaged in discussions with Russian officials regarding diverse areas of collaboration. These include military training and oil exploration.

Russia is also working towards establishing a logistics center on the Red Sea in Sudan. This will strengthen its naval capabilities and strategic presence in the region. Sudan has restated its dedication to Russia in building a naval base on the Red Sea. This development is because of the growing military cooperation between Sudan and Russia, showcasing Moscow’s wider aspirations to enhance its military influence in strategic African nations.

According to experts, there is concern that Russian armed groups are taking advantage of migration routes, specifically those that pass through the Sahara. This exploitation could potentially result in a rise in irregular migration towards Europe. Russia may be seeking to create instability in European nations by intensifying the refugee crises, with the intention of impacting elections and weakening support for Ukraine.

Russia is also actively pursuing economic engagements and resource extraction deals in Africa. Russian officials explored cooperation on infrastructure and natural resource projects, particularly in Chad, Mali, Niger, Sudan, and the Democratic Republic of the Congo. Russia also sought to dominate the uranium market by acquiring assets in Burkina Faso and Chad. President Vladimir Putin’s strategy to support local regimes, coups, and insurgencies facilitates these economic engagements, as evidenced by recent developments in West Africa.

Furthermore, Russian paramilitary groups, particularly the Wagner Group, or as it is now known, Africa Corps, remained active in supporting local regimes and insurgencies with activities in different African nations, including Sudan, Burkina Faso, the Sahel, the Central African Republic, and Libya. In Libya, for example, Russian forces protect oil and gas interests, which constrains Western access and increases European dependence on Russian energy.

Regardless of the obvious fact that Russia, along with China, has a strategic interest in controlling Africa’s natural resources, Russia has a clear objective of countering the West’s influence in Africa. The impacts manifest on several fronts.

First, when it comes to strategic military positioning, cementing the presence of its paramilitary forces while also establishing military bases and logistical centers in key African locations enhances Russia’s ability to project power and influence regional dynamics—potentially disrupting Western naval operations and trade routes.

Second, by exploiting African migration routes to Europe, Russia can create social and political instability within the EU countries, thus influencing elections and weakening public support for EU policies, including sanctions against Russia and support for Ukraine.

Russia’s investments in African natural resources also provide alternative revenue streams and reduce the impact of Western economic sanctions. Control over critical minerals and energy resources increases Russia’s leverage in global markets, including control of gold mines in Sudan and oil exploration endeavours in various African nations. Russia’s expansion of influence through military cooperation has benefited the latter. Strengthening military cooperation with African nations did indeed help Russia build a network of supportive regimes, limiting Western influence in these countries. Furthermore, by forging closer ties with African countries, Russia is proving successful in undermining Western diplomatic efforts in the region, complicating Western economic strategies, and creating votes and positions in international forums that align with Russian interests.

Russia’s specific involvement in Libya is also important to consider. Controlling significant oil and gas resources is the central focus of Russia’s presence there. By maintaining influence over Libyan oil fields, Russia will constrain Western access to these resources and increase European dependency on Russian energy supplies. The increasing presence of its paramilitary Wagner Group, which is influencing and supporting strongly armed factions within Libya and safeguarding Russian interests, cements this control.

This involvement includes securing key infrastructure and providing military support to local allies. Russian involvement in Libya includes smuggling oil and gas, generating revenue, and undermining EU efforts to cut off Russian energy imports.

Another critical aspect is Libya’s role as a transit point for migrants heading to Europe, which allows Russia to influence migration flows and destabilize European nations—exacerbating the refugee crisis. Overall, Libya’s strategic location on the Mediterranean Sea provides Russia with significant geopolitical leverage, allowing it to project a threat into the Mediterranean and challenge the North Atlantic Treaty Organization’s presence.

The actions of Russian paramilitary groups in different African countries, along with their emphasis on safeguarding Russia’s economic interests, are fuelling the rise of terrorism in the region. The growing presence of Russian forces is already exacerbating regional conflicts and heightening local tensions, potentially fuelling the rise of terror groups. This is particularly concerning as organizations with ties to ISIS are gaining momentum in West Africa and the Sahel. The withdrawal of French forces from Mali and Niger, along with the departure of American forces from Niger, resulted in a significant rise in extremist groups in the region. This is having a detrimental impact on the West’s counterterrorism efforts in the region.

Overall, the situation in some African states is proving increasingly worse. The growing influence of Russia comes at the expense of Western powers, resulting in proxy conflicts and potentially destabilizing the continent even more. This can create environments that are conducive to the growth of terror groups. Russia’s manipulation of migration flows can result in worsening the refugee crisis. Terror groups can take advantage of this to bolster influence, bases, and activities in Africa and beyond. The dangers of worsening local conflicts are becoming more pronounced and the escalating violations of human rights in numerous African countries pose a range of intricate consequences that could potentially affect the stability of African.

In short, Russian action in Africa is bad for its inhabitants and bad for the West. At some point the West must counter Russia’s malicious efforts.

Dr. Mohamed ELDoh is a business development and consulting professional in the defense and security sector. Mohamed holds a doctorate degree from Grenoble École de Management-France, an MBA from the EU Business School-Spain, and an Advanced Certificate in Counterterrorism Studies from the University of St. Andrews, UK. Views expressed in this article are the author’s own. 

Russia’s Influence in Africa: Understanding the Big Picture was originally published on Global Security Review.

Clearing the harbor of the collapsed bridge and debris requires the removal of containers from the Dali so that it can be towed away, as well as the removal of wreckage, section by section. Meanwhile there are 11 large ships stuck in the port until the main channel opens. With the primary channel only 50 feet deep, the wreckage blocks all large vessels from entering the Port of Baltimore. On April 28 the first container ship since the wreck passed through a temporary channel.

A deeper channel was opened May 10, and the permanent channel is expected to reopen by June. The Navy is relying on contractors to bring cranes in to remove the salvage.

Since the incident, many naval and shipping experts have chimed in on social media about the state of our Navy and Army Corps of Engineers. There is a concern about the military’s lack of capacity to conduct salvage operations without contractors.

As good ports are determined by geography, there are only so many options for the US Navy. Naval bases are in enclosed bays, such as Puget Sound, San Diego, and San Francisco. Nearly all of them are located behind a bridge that crosses the mouth of their respective bays.

There are five major naval bases behind narrow passageways, and three that are easily obstructed by an unassuming containership. One can find all of these using google maps in minutes. It does not take long to find where the home ports are for American warships or what their deployment cycles look like. The US even has fleet trackers that are posted on social media. Using this information alone, one can estimate how many ships are in port at any given time, and their state of readiness. There is no need for satellite surveillance.

According to the International Chamber of Shipping, there are 1.8 million seafarers worldwide. Most come from China, India, Indonesia, the Philippines, and Russia. Two of those nations are adversaries. The largest ocean carrier, Mediterranean Shipping Company, has more than 700 ships and a long history with Balkan drug cartels. The largest cocaine seizure in US history took place on one of their vessels, as did many other massive drug busts.

This begs the question: is it really impossible for a small number of Chinese-flagged container ships to obstruct the entrance to critical ports, trapping most of the US Navy in port and isolating approximately one-fourth of the Navy from reinforcement and resupply? Such an event would be the modern analogy to the Battle of Gravelines or Red Cliffs, with the Pacific becoming a vacuum for an up-and-coming naval power—China.

America’s allies throughout the Pacific would suffer. It is impossible to maintain logistical supply lines in the Pacific without the Navy. A modern container ship can carry up to 400,000 tons of cargo. The Air Force’s 52 C5 Galaxy cargo aircraft and 275 C17s carry a combined cargo of 25,975 tons. It is far more efficient and practical to resupply by sea.

The US Navy may have the best radar, the best anti-ship missiles, and the best crews, but the fleet only has so much food, fuel, and firepower. Unfortunately, US Navy logistics capabilities were completely gutted, including prepositioned stocks. On top of that, as seen with the USS Boxer’s recent breakdown, the Navy has limited dry-dock capabilities for repairs.

In light of the Dali disaster and the US Navy’s present capabilities, it is time to reassess the security of American ports from asymmetric or even conventional attack. They are simply more susceptible to attack than at any time.

After the War of 1812, the Fortification Board was created to plan for coastal defenses. From then until World War II the Army Corps of Engineers occupied their time with coastal defense. This is no longer their focus—or any other federal agency’s focus. This leaves the nation vulnerable to an unexpected attack.

The United States’ position in the world is a result of American economic strength, a strong military, and a commitment to the freedom of navigation. Adversaries do not share these values and seek to change the status quo. Times have changed, and so have the means and methods of adversaries to harm the United States.

First, it was foreign port security after the USS Cole bombing. Then it was airline security after the attacks of September 11, 2001. Now, the nation must adapt its capabilities and defenses to secure ports and entryways—before an attack has a catastrophic effect. This will require investment in time and treasure, as well as a shift in strategic thinking. The payoff is preventing a larger Pearl Harbor. The time to act is now when costs are at their lowest.

Michael Fincher is a Fellow at the National Institute for Deterrence Studies. The views expressed in this article are the author’s own.

Fixing the Nation’s Harbor Security was originally published on Global Security Review.