The neutral and peaceful Swiss nation this week unintentionally launched what surely has to be one of the most friendly, non-violent and shortest invasions in European military history.

A Swiss army unit accidentally invaded its neighbour to the east on Wednesday, when a 171-strong Swiss company advanced two kilometres into Lichtenstein during a nightly routine training exercise in the Alpine forests in the border area.

The company commander led his men in the wrong direction in bad weather but gave the immediate order to return when realising the error.

"It was all so dark," one soldier told the Swiss newspaper Blick.

The Lichtenstein authorities responded to the incident in a light-hearted spirit, and disclosed to international media that they first got knowledge of the incident after Swiss authorities notified them of what had happened.

"It's not like they invaded with attack helicopters", Markus Amman, a spokesman for the Lichtenstein authorities said in a statement.

The small independent principality of Lichtenstein has a population of only 36 000 citizens, and no army, so the incident was not in any danger of sparking off a military border-strife.

This is however not the first incident between the two European countries during a military exercise in the border area.

During a military exercise in 1985, Switzerland fired several rockets that went astray and set a forest ablaze on the other side of the border. The incident then resulted in Switzerland paying compensation to Lichtenstein for the damage.