In 1759, Putnam led a regiment into The Valley of Death in the attack on Fort Carillon; and, in 1760, he was with the British army that marched on Montreal. In 1762, he survived a shipwreck during the British expedition against Cuba that led to the capture of Havana. Major Putnam is believed to have brought back Cuban tobacco seeds to New England, which he planted in the Hartford area. This reportedly resulted in the development of the renowned Connecticut Wrapper. In 1763, during Pontiac's Rebellion, Putnam was sent with reinforcements to relieve Chief Pontiac's siege of Fort Detroit.