To plan the size of the US military, Pentagon officials rely on what is known as a force-sizing construct, which reflects the upper limits of what the military is able to do. Most famously, in the wake of the Cold War, Pentagon planners relied on the two-war standard, which called for a military sized to fight two near-simultaneous wars if necessary. But in recent years, the two-war standard has been watered down even as demands on US forces have grown. Not only has it been scaled back, but the force-sizing construct also diminished after it was exposed as inadequate to meet the demands placed on the military in the aftermath of 2001 in both Iraq and Afghanistan.

Yet returning to a true two-war standard is a necessary but insufficient step to create a modern force-sizing construct. Rather than only incorporating demands for forces in wartime, the Pentagon’s construct must also include regular peacetime demands on US forces. While steady-state demands such as forward presence abroad, training missions with partner militaries, and rotational deployments do not rise to the magnitude of major contingency operations, they form the backbone of day-to-day US military activities. Moreover, they serve a vital role in shaping the international environment to advance American interests, preserving a norm-based international order, reassuring allies, and deterring potential aggressors.

These peacetime missions represent the most cost-effective and preferred use of American military power. They magnify all other aspects of American national power while upholding stability in vital regions. Only by moving to a force-sizing construct that allows the United States to fight and win two near-simultaneous major wars—while also conducting the multitude of everyday operations that promote global stability—can defense planners more accurately size and budget for the demands on the US military...

Read the full article at the American Enterprise Institute: US military force sizing for both war and peace