War stimulates the economy

[KevinTheOmnivore]

It seems the focus has been on World War II, which is a pretty narrow attempt to answer the question.

I think it can be said that specific sectors thrive during war, particularly war industries. Prior to the War of 1812 for example, Treasury Sec. Galadin and Thomas Jefferson theorized that America would never really need a strong navy, so Galadin had the navy stripped down to essentially small gun boats that patroled the shores. He was very fiscally conservative, and figured that America would never get embroiled in a naval war. Oops.

So Madison becomes president, War of 1812 kicks up, British and French piracy, etc. etc., and we have no capable response mechanism. The navy is built up again to fight the war, and (theoretically) they did well. I'd have to research some more to see if any certain companies thrived, though.