The historical pattern is pretty clear. Washington launches a war. Initially, it might not even look like a war. It might be a police action, or combat advisers, or technical assistance, or a humanitarian mission. But then some of those troops are killed or injured, or perhaps other Americans are harmed in the process, and the public rallies to the troops/the flag. Then, once the mission is well along, there is an overwhelming impulse to see that investment through to victory, to recover sunk costs, or to maintain or restore the nation's credibility.
There a number of arguments for why we shouldn't allow sunk costs or concerns about credibility to sustain a military mission that has outlived its usefulness, or that might actually undermine American security (see, for example, Daryl Press's classic). The point here is that the enormous knowledge and power imbalance between the elites and the public at large, combined with the realization within Washington that policymakers can do some pretty stupid things abroad and not pay a heavy political price here at home, tips the scales heavily in an interventionist direction.
In other words, the Founders' concerns have proved valid, but their system for constraining executive power has failed to live up to their expectations. Although the Constitution grants Congress the authority to declare war, and the president the authority to direct it once declared, our responses to recurring crises -- both real and imagined -- have fundamentally altered the balance of power.
But hope springs eternal. Real change is possible if a few of the new members, and a handful of the old bulls, decide to reject business-as-usual, and perhaps to return to an earlier vision of the proper balance between Congress and the Executive, and between the government and the people.
