What does the term "double-tree" describe as it applies to horses or mules?

It has to do with a crossbar that is used for harnessing two horses abreast to a wagon.

Wayne,It's a 2 Horse Wooden Lead Evener (Double Tree) used for the lead team in a 4, 6 or 8 horse hitch. Could this be what you're looking for? ~ScarlettMyDear.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.