This post is part of an ongoing series preparing for the AEI/CNN/Heritage National Security & Foreign Policy GOP presidential debate on November 22^nd.

One of the guiding principles for the U.S. military has been, particularly in the post-Cold War era, the need to be able to undertake missions across “the full spectrum of conflict.” This includes high- and low-end conflicts, as well as combat across land, sea, air, space, and cyber. This measure is not a static one; it evolves with changes in technology, tactics, and the broader strategic environment. And while there are exceptions to the principle of American dominance across the “spectrum of conflict”—namely our recent experience of land wars with an Army too small for the missions at hand—American presidents have grown accustomed to a military able to carry out a wide range of operations. But with the defense budget cuts suffered in recent years, as well as those in prospect this fall, America’s next president may command armed forces that can no longer do more with less.

Grave challenges face each of America’s armed services: the Navy’s size is shrinking while its operational demands increase; the Army and the Marine Corps are on the chopping block for further troop reductions; and the Air Force is aging rapidly. The Army may be the most vulnerable of the services in the near term, and is already working through scenarios of troop reductions. A recent Defense News article indicated that 10 to 15 brigade combat teams will likely be eliminated. All this for a ground force unable on 9/12 to fulfill the Pentagon’s basic “two regional war” paradigm, the term U.S. planners used when building a force ostensibly able to wage two medium-sized wars simultaneously. Two sequential wars later, with a Marine Corps diverted from its core functions, a body of reserves that saw extensive action, marginal top-line troop buildup, and high rates of deployment among active and reserve troops, force levels are again in budget analysts’ cross-hairs. Of course, ground force reductions are as much because of the conflicts of the past decade as in spite of them: Americans do not want to fight more large conventional wars, and understandably so. But just because we don’t want to fight certain types of wars does not mean that we should not prepare for the worst.

President Reagan famously made the case for “peace through strength”; as the presidential debate moves forward, there is rhetorical space for candidates to give clarity and reassurance to Americans in an uncertain world.

Richard Cleary is a research assistant at AEI