Which battle did great Britain lose an entire army 1n 1777?

In 1777, Great Britain lost an entire army at the Battle of Saratoga during the American Revolutionary War. This pivotal defeat, occurring in two engagements in September and October, marked a significant turning point in the war, as it galvanized French support for the American cause. The surrender of British General John Burgoyne to American General Horatio Gates ultimately boosted morale for the Continental Army and shifted the momentum in favor of the revolutionaries.