Hi!
What George Washington did was called "Girdling"
It consists of removing bark, cambium, and phloem from a tree, and leaving only the xylem and heartwood functional.
What it does to the tree is to remove the tissue that is responsible for carrying the sugar from the leaves to the roots. This causes the roots to die, and with them, the tree dies too. This process is very slow and is used by horticulturists to kill trees while giving the environment time to adjust.