I'm always surprised when I hear people say that the war against ISIS can be won, if only it is fought with more vigor. Expanded. Prolonged. Intensified.
It won't happen.
Most people have no idea how hard the US tried to defeat the Viet Mihn ... the US dropped an absolutely insane amount of bombs on Cambodia and Vietnam, triple the tonnage dropped in all theaters in World War II. (source)
Americans pursued mass murder with a psychopathic intensity in Vietnam, Cambodia, and Laos. They sent two millions soldiers over there. They carpet-bombed the countryside, sparing no old man, woman or child. They killed over a million people. Yet, the more they bombed, the more they lost. With every bomb dropped; with every village burned, the US was steadily losing ground in that war for years. For years.
The leading candidate for the GOP nomination for the US Presidential election to be held this November makes appeals to American isolationists by promising to refrain from foreign adventurism and then announces that another 20,000 to 30,000 troops will be needed to "knock out ISIS ... knock them out fast and then we have to get back home."
What American really believes the myth of the quick and easy war? America's current wars have lasted, now, for almost 15 years. They'll last at least another 15.
And, one day, the US defeat will be unarguable. Just like Vietnam.