What Ukraine's Defense Taught the World About Deterrence

On February 24, 2022, Russia launched a full-scale invasion of Ukraine with approximately 190,000 troops, expecting — according to captured operational plans and subsequent Russian military commentary — a collapse of Ukrainian resistance within days. Western intelligence assessments largely concurred: Kyiv would fall in 72 hours.

Nearly four years later, Ukraine continues to fight. Whatever the conflict's ultimate outcome, Ukraine's defense has already rewritten several foundational assumptions about modern warfare, deterrence, and the defense of smaller nations against larger aggressors. These lessons extend well beyond Eastern Europe.

Lesson 1: Pre-Conflict Preparation Is Decisive

The single most important factor in Ukraine's successful initial defense was preparation that began years before the invasion. After Russia's 2014 seizure of Crimea, Ukraine undertook a systematic military reform:

• NCO corps development: Ukraine rebuilt its non-commissioned officer corps along NATO models, creating small-unit leadership capability that proved critical in the chaotic first days of the invasion.
• Western training programs: Between 2015 and 2022, the United States, United Kingdom, Canada, and other allies trained approximately 10,000 Ukrainian soldiers annually through programs like JMTG-U (Joint Multinational Training Group-Ukraine).
• Javelin and NLAW pre-positioning: Anti-tank missiles supplied before the invasion were decisive in destroying Russian armored columns approaching Kyiv. Post-invasion deliveries, while crucial for sustaining the fight, could not have arrived in time to stop the initial assault.
• Communications infrastructure: Starlink terminals, delivered in the war's first days, maintained command and control when conventional communications were disrupted. The infrastructure to integrate them had been partially prepared in advance.

The contrast with the Afghan National Army is instructive. Afghanistan received 20 years of training and equipment but collapsed in 11 days. Ukraine received 8 years of targeted preparation and held. The difference was not resources — it was what was prepared, how, and with what degree of self-reliance built in.

The RAND Corporation's 2023 analysis of the war's early phase concluded that "the marginal return on pre-conflict investment in defense capability exceeded the marginal return on post-conflict emergency supply by a factor of approximately 5 to 10." Every dollar invested in deterrence before February 24 was worth five to ten dollars invested after.

Lesson 2: Geography Is Still the Master Variable

Ukraine's flat terrain — the North European Plain — is among the most difficult defensive geography on Earth. There are no natural chokepoints, no mountain ranges, no significant water barriers between the Russian border and major Ukrainian cities. Historically, armies have swept across this terrain in both directions.

Despite this disadvantage, Ukraine held. This fact carries an important implication for other potential conflict zones with more favorable defensive geography.

Consider the comparative defensive advantages of an island defense scenario:

• Water barrier: An attacker must cross a significant body of water under fire — the most difficult military operation in existence. Ukraine's defenders did not have the advantage of forcing the enemy to cross 100+ miles of open sea.
• Limited landing zones: An island with mountainous terrain and limited suitable beaches constrains an attacker's options to a small number of predictable landing areas. Ukraine faced attack from multiple land borders simultaneously.
• Logistics bottleneck: An amphibious attacker cannot resupply by road or rail — everything must come by sea or air, both of which are vulnerable to interdiction. Russia, despite sharing a land border with Ukraine, still suffered critical logistics failures.
• Air superiority challenge: Defending an island from 100+ miles away requires achieving air superiority over water — far more difficult than over adjacent land territory, as there are no forward airfields and combat aircraft face extended transit times.

If Ukraine — on the most invasion-friendly terrain in Europe — could hold against a numerically superior force, the defensive calculus for an island with natural geographic advantages is significantly more favorable. This is not opinion; it is a straightforward application of military geography principles taught at every staff college in the world.

Lesson 3: International Unity Is a Force Multiplier

The speed and scale of the international response to Russia's invasion surprised virtually every observer — including, evidently, the Russian government.

• Economic sanctions: Coordinated sanctions froze approximately $300 billion in Russian central bank reserves and cut major Russian banks from the SWIFT financial messaging system. The ruble lost 50% of its value in the first week.
• Military aid: As of late 2025, Western nations have committed over $200 billion in military and economic assistance to Ukraine — a figure that exceeded pre-war expectations by an order of magnitude.
• Intelligence sharing: Real-time intelligence from Western satellites and signals intelligence provided Ukraine with a persistent information advantage throughout the conflict.
• Diplomatic isolation: Russia faced unprecedented diplomatic isolation, with 141 nations voting to condemn the invasion at the UN General Assembly.

However, this unity had critical limitations. Support was reactive, not proactive. Weapons systems were delivered incrementally, with each escalation in capability (tanks, long-range missiles, F-16s) requiring months of political deliberation. The "boiling frog" approach — gradually increasing support to avoid escalation — may have been strategically prudent, but it meant that Ukraine fought with one hand tied behind its back for extended periods.

The lesson is dual-edged: international unity works as a force multiplier, but its effectiveness is proportional to its speed. A CSIS analysis found that weapons systems delivered in the first 30 days of conflict had approximately three times the operational impact of the same systems delivered after 180 days — because early deliveries shape the conflict's trajectory, while late deliveries merely sustain it.

Lesson 4: The Will to Fight Is Not Optional

Western analysts had systematically underestimated Ukrainian will to fight. Pre-invasion polling by the Kyiv International Institute of Sociology found that 57.5% of Ukrainians expressed willingness to resist armed aggression — a number many Western analysts dismissed as aspirational.

In practice, the actual figure proved higher. Ukraine mobilized effectively, with hundreds of thousands volunteering for territorial defense forces. Civilian resistance — from blocking tank columns with their bodies to providing real-time intelligence via smartphone apps — supplemented military operations.

This factor is frequently overlooked in quantitative military analyses, which tend to focus on equipment counts and force ratios. Ukraine demonstrated that a population's determination to defend its sovereignty is a strategic asset of the first order — one that cannot be manufactured from outside but can be cultivated and supported.

Polling data from other nations under potential threat shows comparable patterns. Taiwan's Institute for National Defense and Security Research has documented rising public support for defense — from approximately 40% expressing willingness to fight in 2018 to over 70% in 2024, a shift driven substantially by observing Ukraine's example.

Lesson 5: Asymmetric Capabilities Change the Calculus

Ukraine's effective use of relatively inexpensive weapons systems against vastly more expensive platforms has restructured defense economics:

• Javelin anti-tank missiles ($178,000 each) destroyed T-72 and T-80 tanks ($2–3 million each) at ratios that make armored assault economically prohibitive.
• TB2 Bayraktar drones ($5 million each) destroyed air defense systems, logistics convoys, and naval vessels worth 10–100 times their cost.
• Naval drones — Ukraine's domestically developed unmanned surface vessels, costing an estimated $250,000 each — sank or damaged multiple Russian naval vessels including the cruiser Moskva's escorts, effectively denying Russia naval dominance in the western Black Sea without Ukraine possessing a single major warship.
• HIMARS precision artillery systematically destroyed Russian ammunition depots and command posts at ranges that kept the launchers beyond effective counter-fire.

The implications for island defense are significant. An island defender can employ anti-ship missiles, naval mines, shore-based anti-aircraft systems, and unmanned systems to impose costs on an amphibious attacker that far exceed the defender's investment. The cost-exchange ratio — the cost the defender imposes on the attacker per dollar spent — is inherently favorable to the defender in an amphibious scenario.

Lesson 6: Information Warfare Is a Domain

Ukraine's information campaign was arguably as effective as any weapons system. President Zelensky's nightly addresses, distributed globally via social media, maintained international attention and political support for aid packages. Crowd-sourced intelligence from civilians supplemented military reconnaissance. Russian disinformation campaigns were systematically countered by open-source intelligence communities.

The lesson: in the modern information environment, a defender's narrative can become a strategic asset. Global public opinion influences aid decisions, sanctions enforcement, and diplomatic support. A nation that can tell its story effectively to the world gains a significant strategic advantage.

The Pre-Conflict Window

Perhaps the most consequential lesson from Ukraine is about timing. The critical investments that enabled Ukraine's defense — training, pre-positioned weapons, communications infrastructure, alliance relationships — were made before the first shot was fired.

Once a conflict begins, the physics change. An island cannot be resupplied as easily as a nation with land borders. Air and sea corridors must be established and defended. Pre-positioned supplies are the only supplies available in the critical first days and weeks.

The data from Ukraine is unambiguous on this point: deterrence investments made before a conflict are orders of magnitude more effective than equivalent investments made after one begins. The window for preparation is finite, and it closes when the first missile launches.

Whether that window is being used effectively — in any given potential flashpoint — is a question the data invites but does not answer. That judgment belongs to policymakers, military planners, and informed citizens.

Further Reading

• Why Taiwan Is Nearly Impossible to Invade: A Military Analysis
• What History Tells Us About Abandoning Strategic Allies
• Inside China's Military Modernization: What the Numbers Tell Us