Swiss the Invading Army

On 5 December 1985, rockets fired by the Swiss Army landed in Liechtenstein, causing a forest fire. Compensation was paid.[source]

On 13 October 1992, following written orders, Swiss Army cadets unknowingly crossed the border and went to Triesenberg to set up an observation post. Swiss commanders had overlooked the fact that Triesenberg was not on Swiss territory. Switzerland apologized to Liechtenstein for the incident.[source]

In March 2007, a company of 171 Swiss soldiers mistakenly entered Liechtenstein, after taking a wrong turn in the darkness. The troops returned to Swiss territory before they had travelled more than 2 km into the country. The Liechtenstein authorities did not discover the "invaders", and were informed by the Swiss after the incident. The incident was disregarded by both sides. A Liechtenstein spokesman said "It's not like they invaded with attack helicopters".[source1] [source2]