Berga Naval Base

From 1904, Hårsfjärden began to be used more permanently as a base for the Coastal Fleet's combat and signal schools and for naval mine training and more.

The bay between Vitsgarn and Märsgarn became an important naval port where seaplane and submarine facilities were built.

In 1944, the Riksdag decided that the Swedish state would acquire Berga Castle after the late and large landowner Helge Ax:son Johnson.

The area included a strip of water that stretched from Vitså harbor to Näringsberg and was 3.5 km long and 800 meters wide.

On 21 October 1946, His Royal Highness Crown Prince Gustaf Adolf performed the inauguration of the Swedish Navy Non-Commissioned Officers' School.

In 1948–1949, the Submarine and ASW School (Ubåts- och ubåtsjaktskolan) began training at Berga for both commanders and conscripts.

Following the Defence Act of 2004, Berga Naval Base is the training ground for the 1st Marine Regiment and the location of the Home Guard unit Södertörn Group (Södertörnsgruppen).