He was the son of Ebenezer and Deborah Haynes Learned, and was born at Oxford, Massachusetts, and lived his entire life in the area.
Learned was an active member of the local militia, and raised and drilled a company at Oxford during the French and Indian War.
He remained active in the militia, and led his own and a neighboring company of minutemen to Boston, where he received the news of the Battle of Lexington on April 19, 1775.
By the end of the Siege of Boston, General Washington had given Learned command of the important Dorchester Heights position.
He led a battalion of 500 specially selected men, to clean out the traps, abatis, caltrops, and garbage left by the British.
At the Battle of Bemis Heights his brigade was in the center of the left division, fighting alongside Daniel Morgan and Enoch Poor.
The attack on the American far left was turned by Daniel Morgan's men, but the enemy's center was held by Hessian troops.