Humpton purchased a captain's commission in the Royal Army and fought in the Raid on St Malo during the Seven Years' War.

At the beginning of the American Revolutionary War he offered his services to the patriot cause and was named a lieutenant colonel in 1776.

Tasked with collecting boats on the Delaware River, his attention to this assignment materially helped the Americans win the Battle of Trenton in December 1776.

After bringing charges against Anthony Wayne for Paoli, he led the 2nd Brigade at Germantown in October.

Humpton died in 1804 and was buried in the Friends Meeting cemetery in Caln Township, Chester County, Pennsylvania.