Americans should never forget that our own system rests on two acts of revolution . . . The United States has revolution in its DNA and AmericaÂ’s deepest values tell us that revolutions like those in France, Russia, Iran and Egypt are the last defense of humanity against the establishment or the perpetuation of tyranny.

All of this is true; none of this helps American governments figure out what to do when revolutionary upheaval breaks out in a key foreign ally. It is almost never the right choice to help the challenged government cling to power by using American forces and resources to crush the uprising.

Yet distancing ourselves from a weakening ally is not always cost free.