There is a lesson we should have drawn from Vietnam - don’t start a war you don't intend to fight vigorously enough to win. We did not learn from Vietnam and we repeated it in Iraq and Afghanistan. We won Vietnam on the ground, but tossed it away politically. Ditto, in the recent wars.
A war must continue until the opponents will to fight is totally and completely vanquished. The Civil War is a example, Grant and Sherman pressured Lee until he could no longer resist. WWI begat WWI as we entered into an armistice, not a surrender. Germany was quick to rearm and start again.
Japan and Germany were fought to the ground in WWII and emerged as democracies.
60 years after the cease fire in Korea, North Korea remains totalitarian and belligerent.
Until we kill almost every Salafi, we will remain in danger from attack. They are just as fanatical as the Japanese were in prior to and during WWII.