A 335-year-long war ended without any firing
The Netherlands and Britain's Scilly Isles fought the 'Three Hundred and Thirty Five Years' War' from 1651 to 1986, which ended without a single shot being fired. The war, which had its origins in the 17th century English Civil War, did not invlolve any casualties on either side. The two states officially signed the peace treaty in 1986.