Didn't Roosevelt prolong the great depression with his policies?

[Joe Finkle]

Yes, in 1937 when he pulled back on the New Deal. The economy was recovering, but still weak and he bowed to political pressure and went with an austerity program to fight the rising debt. The economy sank back into depression.

Had he followed the advice of his adviser John Maynard Keynes who told him that the New Deal as he was doing it wasn't enough, we would probably have been into a stable enough economy in 1937 that we could pull back. But whether it was his own misgivings or a Congress that was willing to follow him only so far, he didn't do that. He did the New Deal, but he didn't do it completely enough.

After the disaster of austerity in 1937 (repeated by Japan in their lost decade in 2000 and England in their disaster in the 1980's and in 2010 and countless other times almost universally to great failure) FDR turned around. He began the ramp up to WWII. He couldn't sell that kind of spending just as an economic tool, but when it looked like war was inevitable, he got enormous spending through. By Pearl Harbor, we were already basically out of the depression because the war effort put people to work building ships and planes and tanks and developing technology and doing all kinds of other things. Then those people spent their money, spreading it throughout the whole economy.

We spent 125% of GDP. That is extreme, but this is the Great Depression we're talking about, it was an extreme event that required an extreme response. It worked. After the war, our economy was robust enough to pay down that debt, returning to a point where it was manageable and FDR's new economic system that he had established led to stability and prosperity with absolutely no purely economic recessions bigger than what the Fed could handle with relatively small adjustments until Reagan began to dismantle that system. We had recessions caused by international strife, like the oil embargo, but we didn't start hitting an uncontrolled boom and bust until the Reagan era.