From Wikipedia: The Tuba War of 1908 lasted for 4 days between Estonia and Latvia. It was quickly ended by neighboring countries when they couldn't sleep at night due to the constant noise. Armies from Lithuania, Russia, Finland, Belarus, and the 3rd.Deaf Battalion from Denmark assisted in quelling the war.
The death count extended to four people, two from each side. The countries counted it as a draw, though each claimed it as a victory.