When asked what the response should be as to why the US military is stationed in Europe, a burly American airman succinctly replied, “I would tell them to read a history book.” This sentiment underscores an enduring truth: as much as Presidents Woodrow Wilson and Franklin Roosevelt sought to keep the US out of foreign wars, both eventually recognized that America's national security interests required engagement in Europe. A young US Air Force technician added a modern perspective: “Aren’t our enemies gathering? Don’t we need friends?”

This need for engaging allies and watching adversaries is more pressing than ever. According to the recent Commission on the National Defense Strategy report, the US must be prepared to simultaneously address threats in the Indo-Pacific, Europe, and the Middle East. The report warns that America is not fully prepared to confront this challenge. To meet multi-theater threats from authoritarian powers that are increasingly coordinating, America must not only rapidly modernize its military, but it must also strengthen its alliances— NATO chief among them. 

The good news is that NATO has come a long way toward strengthening itself in recent years. While more significant steps are required, NATO is stronger today than many perceive. Its European members have not only stepped up to higher defense spending, but they have also committed to make significantly more troops available on short notice, deployed them forward in new areas and in larger formats, adopted a more rigorous defense planning process to define what resources the risk requires, improved readiness, and made initial steps on interchangeability. 

Rising Defense Spending

In 2024, 23 of 32 NATO allies are expected to meet or exceed the 2% of gross domestic product (GDP) target set at the 2014 Wales Summit, with nations such as Poland and the Baltic states leading the charge. At the height of the Cold War, NATO members spent an average of 3.5% of GDP on defense. Today, Poland, with a defense spending rate of 3.9% of GDP, is highest among NATO members. It earmarked 4.7% for this year and supports President Donald Trump’s proposal to increase NATO defense spending to 5% of GDP. 

Generally, defense spending is correlated with the proximity of countries to Russia, with Belgium, Canada, Italy, and Spain below the 2% threshold. Since the US is even farther from Moscow, it welcomes Secretary General Rutte’s efforts to get  all allies to meet the funding pledge.

Force Structure and Readiness

Higher funding is resulting in more boots on the ground. At the 2022 Madrid Summit (soon after Russia’s invasion of Ukraine), the alliance significantly increased the number of troops that were on call on short notice. Their numbers rose from the 25,000 troops organized as the NATO Response Force (deemed appropriate when fighting terrorism) to up to 500,000 to meet the Russian menace.  Allies agreed to a new NATO Force Model, able to muster well over 100,000 Tier 1 Forces in up to 10 days, Tier 2 Forces that raise the total forces on high alert (available around 10-30 days) to around 200,000 with another 300,000 Trier 3 Forces (for a total of 500,000) on call within 30-180 days. These represent the national forces that would be available to the NATO Command. 

Defense Planning Process

And NATO also committed that resources should match the need. In February 2023, NATO defense ministers approved the NATO Defense Planning Process (NDPP). This framework begins with political guidance, which NATO military leaders use to determine the Minimum Capabilities Requirements necessary for alliance forces to address current threats. These requirements are shaped by evolving Regional Defense Plans (North Atlantic and Arctic, Eastern Europe and the Baltics, Mediterranean and Black Seas). The requirements are designed to ensure NATO can defend "every inch" of its territory. Once established, these requirements are "apportioned" among member nations, with specific targets set for each ally to achieve.

This process aims to align contributions of individual nations into a cohesive whole, ensuring the alliance meets the rigorously vetted demands of its military plans. Importantly, the alliance needs define how much members must spend. This effort is underscoring the growing need for increased defense spending. Addressing speculation that NATO may increase its defense spending target to 2.5% of GDP in the short term and possibly 3% by 2030, NATO Secretary-General Mark Rutte highlighted the financial reality: "When you look at the capability targets, [when] you look at the gaps still there . . . it is clear that, with 2 percent, you cannot get there."

Forward Deployment

NATO has also taken steps to ensure its members are positioned effectively against threats in sufficient numbers and maintained at a high state of readiness. At the 2022 Madrid Summit, NATO increased the number and locations of its forces deployed on its  eastern flank, integrating modern strategies and technologies to enhance its effectiveness.

In direct response to threats along NATO's eastern flank, eight multinational battle groups, led by Canada, France, Hungary, Germany, Italy, Spain, the United Kingdom, and the US, now maintain a rotational presence in the Baltic states and Poland. 

Under the "Framework Nations Concept," NATO has evolved from merely "pooling and sharing" resources to forming structured groupings that pair larger and smaller allies. This approach optimizes complementary and niche capabilities, allowing nations to contribute more effectively to collective defense. The notion of tripwire forces has evolved to focus on credibly defending all NATO territory on the eastern flank. 

To further enhance coordination, NATO is seeking to have its Regional Defense Plans align national and collective defense efforts. One notable national-level initiative is the "Military Schengen" zone, announced by Poland, Germany, and the Netherlands. This agreement facilitates the rapid mobilization of forces across key terrain, addressing the need for swift and flexible troop movements.

Readiness

Forward-deployed forces alone do not guarantee credible deterrence; they must be rigorously trained to operate effectively against realistic and evolving threats in demanding scenarios. NATO has made significant strides in demonstrating and enhancing this readiness through large-scale exercises. From January to May 2024, Steadfast Defender brought together 90,000 troops from all NATO member states, marking the largest NATO exercise in decades. This exercise showcased the alliance’s ability to not only repel an initial attack, but also to project the full force of transatlantic military power across contested domains (land, air, sea, and space) even while under attack.

Building on this momentum, upcoming exercises such as Steadfast Dart 2025 and Griffin Lightning 2025 will focus on rapidly deploying allied forces to NATO’s eastern flank, testing their alignment with Regional Defense Plans. National exercises such as Hedgehog 25, Defender Europe 25, and BALTOPS 25 further enhance interoperability by validating the ability to deploy, integrate, and operate multinational forces effectively in defense of NATO’s strategic objectives.

These efforts, spanning the full spectrum of military operations, ensure that NATO forces remain prepared for the fast-evolving tactics and capabilities of potential adversaries. By continually evaluating and refining its plans through realistic training scenarios, NATO reaffirms its commitment to maintaining a credible, adaptable, and united defense posture.

From Interoperability to Interchangeability

While NATO is also focused on interoperability—allowing NATO forces to operate together effectively—this is an area where significantly more progress is required. While the US operates 33 major weapons systems, European nations maintain 174, creating inefficiencies that hinder joint operations. Historically, national armament priorities overshadowed unified defense needs, but the war in Ukraine has exposed the risks of this fragmentation.

NATO must now advance toward not just interoperability but interchangeability, where systems from different nations are functionally identical and seamlessly shareable. This shift would enhance logistical flexibility and ensure sustained operations during protracted conflicts.

Recent progress includes the 2023 NATO Defense Production Action Plan and the 2024 NATO Industrial Capacity Expansion Pledge, which aim to align defense industrial efforts across the alliance. To face future threats, NATO must prioritize interchangeability and strategic industrial coordination at the alliance level (not just within Europe) to foster deeper unity and operational resilience.

Conclusion: Strengthening the Alliance

The organizational changes in recent years in force structure, forward deployment, and readiness are profound. They amplify the impact of higher defense spending. Yet more needs to be done, including all members agreeing to and meeting higher defense spending levels, industrial base expansion, and greater interchangeability. Recent progress gives hope that higher levels of capabilities can be achieved.

As both Europe and America grapple with balancing security and prosperity, it is worth remembering that NATO was founded to address this very challenge. While not perfect, NATO has been overwhelmingly successful in its mission to deter war and contain conflict, benefiting the US, Europe, and the world. 

As Benjamin Franklin warned at America’s founding: “We must all hang together, or ... we shall all hang separately.” Today, that sentiment resonates as strongly as ever in the trans-Atlantic Alliance.

Hon. Mark Kennedy is Director of the Wilson Center’s Wahba Institute for Strategic Competition, Senior Fellow at CNA - Center for Naval Analyses, President of the University of Colorado and a former Member of Congress from Minnesota.

Col (ret) Jeremy “Maestro” Renken is a former Air Force F-15E pilot and Squadron Commander who trained and operated with NATO forces during two assignments to Europe and five combat deployments. 
 

The views expressed in this article are those of the authors and do not reflect the official policy of position of the Department of Defense or the US Government.