Preparing for the next war has always been difficult. Among other challenges, planners must wrestle with imperfect information, cognitive biases (such as fighting the last war), and frequently ambiguous public support and political guidance. While all of these impediments can exist during wartime, they are exacerbated by peacetime conditions. Even the most basic questions, such as who will be the enemy, are often unknowable until the shooting starts. What’s more, unlike during wartime, the lack of immediate feedback as to what is and is not working means one can never be too confident in one’s predictions. Developing new doctrine, weapons systems, and strategy in such a context is incredibly hard. Planning for the next war, therefore, is a bit like trying to assemble an unknown puzzle while blindfolded. You can get a feel for the pieces, but you’re really not sure what it is you’re assembling.
As a result of these difficulties, even the best planners end up making little better than educated guesses. It’s no surprise then that the United States has been wrong time and again as to what the next war will look like and then been unprepared to fight it. As former Secretary of Defense Robert Gates noted in an address to the cadets at West Point:
When it comes to predicting the nature and location of our next military engagements, since Vietnam, our record has been perfect. We have never once gotten it right, from the Mayaguez to Grenada, Panama, Somalia, the Balkans, Haiti, Kuwait, Iraq, and more – we had no idea a year before any of these missions that we would be so engaged.
Peacetime planning, therefore, requires a constant balancing act between preparing for what you believe will be the next war and maintaining just enough flexibility in your force structure to accommodate alternatives in case your prediction is wrong. Ideally, the point selected on this scale represents a reasonable compromise between capability, cost, and risk tolerance. However, recent trends in weapons procurement have made finding this point even harder than it was in the past. Specifically, the decades it takes to field new weapons systems means planners can no longer count as heavily on innovating during wartime to overcome major capability gaps and weaknesses.
Take, for example, strategic bombing in World War II. At the beginning of the war, the U.S. Army Air Corps believed that daylight, un-escorted bombing of Germany would reap significant benefits at little cost. Air Corps leaders believed that heavily armed bombers, such as the B-17, would be able to defend themselves against German interceptors as long as they flew in the proper formation. When this assumption proved false and losses started mounting, the Air Corps was forced to search for an escort fighter that had both the ability to beat Germany’s tactical aircraft and the range to accompany the bombers all the way from the U.K. Thankfully, such a plane had been quickly developed just a few years earlier: the P-51 Mustang.
The P-51 was the product of British interest in developing an American source of fighter aircraft for the RAF. In addition to its amazing performance, one of the most spectacular things about the Mustang was the speed at which it was developed, tested, and then procured. The first prototype aircraft was rolled out on September 9, 1940, just 102 days after the contract was signed. The first test flight took place a month later on October 26 and the plane was officially introduced into RAF service in January 1942. In total, the plane went from the drawing board to wartime service in under two years, allowing it to be available as an escort fighter when the US Army Air Corps came searching.
Such a story is highly unlikely today. Modern weapons are so complicated, and the development and procurement bureaucracies so cumbersome, that new programs can take decades to bear fruit. This poses the question of what the United States could do if it found itself facing a major capability gap in a future war. Changes in doctrine and quick upgrades to existing systems could potentially fill some new requirements, but there’s a limit to how far such changes could go. At a certain point, you cannot turn a tactical fighter into a strategic bomber, or an armored personnel carrier into a main battle tank.
Given this fundamental reality, it is more important today than ever that the United States fields the proper military equipment prior to the start of conflict. This means that peacetime planning should be far more humble and risk adverse. The United States’ poor track record of predicting future wars, and the long time it takes to develop new systems, should caution policymakers and planners from over-investing in any one system or vision of the future at the complete cost of others.
Most significantly, these facts suggest that the United States should spend significantly more money on defense than it currently does. The Pentagon requires more money if it is to be prepared to fight and win a wide variety of wars. A larger budget would reflect not only U.S. strategic responsibilities but also the increasing difficulty of counting on wartime innovation to make up for peacetime compromises.
Donald Rumsfeld famously said you go to war with the army you have, not the army you might want. While this adage has always been true, its significance has grown as weapons systems have become increasingly difficult to develop and procure. As such, peacetime planners and policymakers should accept less risk and increase the funding available to the military. Otherwise, the United States risks being incapable of winning the wars of the future.
 In his book The Accidental Guerilla, David Kilcullen recounts a lecture he received in early 2001 as a student at the Australian Defense College from a retired American general. The general spent two hours explaining how the air campaigns in Bosnia and Kosovo, the stabilization missions in East Timor and Sierra Leon, and the humanitarian mission in Somalia had proven the obsolescence of ground warfare. He urged the students to focus on the Revolution in Military Affairs (RMA), promising them that technological advancement was the key to future success.
This prediction, of course, proved disastrously wrong. The RMA-inspired offensive in Afghanistan just a few months later proved capable of ousting the Taliban, but was ultimately unable to bring lasting peace to the country or strategic victory for the United States. Likewise, the invasion of Iraq demonstrated the continued necessity of ground forces in 21st century combat. Having bet heavily on one vision of the future, the United States paid a high cost when events turned out otherwise.
 For example, the decision to prematurely stop procurement of the F-22 because it was useless in Iraq and Afghanistan now appears shortsighted as concerns over China’s rise and modernization grow.