In 1866, during the Austro-Prussian War, Liechtenstein sent 80 men to guard a mountain pass. They saw no fighting at all. When they marched home, they had 81 men because they brought back a new friend they met along the way!

In the mid-19th century, wars were usually bloody and tragic. However, the tiny nation of Liechtenstein managed to have a military campaign that sounds like a heartwarming comedy.
In 1866, during the Austro-Prussian War, Liechtenstein deployed an army of exactly 80 soldiers. Their job was to guard the Brenner Pass between Austria and Italy.
While the rest of Europe was fighting, the soldiers from Liechtenstein sat in the beautiful mountains, enjoying the scenery and fresh air. They saw absolutely zero combat. Not a single bullet was fired, and not a single drop of blood was spilled.
When the war ended and the troops marched back home to the capital, Vaduz, the locals counted them. Instead of 80 men, there were 81.
This was the only military unit in history to suffer "negative casualties." Shortly after this "success," Liechtenstein disbanded its army entirely, deciding they didn't really need one. To this day, they remain one of the few countries in the world with no standing military.