What do Quakers believe about war and serving in the military?

It seems that I once heard that [Quakers](https://en.wikipedia.org/wiki/Quakers) are pacifists, but I'm not sure if that's just a rumor or not. What is the Quaker doctrine regarding war and killing people as a soldier in the military? If they think it is wrong, what is the biblical basis for this belief? Also, do their beliefs extend to being a soldier in the military under any capacity (such as a chaplain, for example)?