searchlights were first used at viapori during the russo-turkish war in 1878, and they were originally intended for guarding the controlled mine barriers. during the first world war fortified searchlight positions were part of the coastal forts. the main line of defence had larger two searchlights at rysäkari and kuivasaari and an additional six smaller searchlights beside them and on the other islands. miessaari 150 cm searchlight position was not completed during the war. in the second line 150 cm searchlights were used on kuninkaansaari and vallisaari, while other forts had or searchlights. diesel generators provided the necessary electrical power to operate the searchlights. searchlights were used in disappearing positions, where the searchlight was normally in a shelter and only exposed when needed for illumination. the disappearing positions had two types: either the searchlight was raised from the shelter by a lifting mechanism, or it was moved by rails from the shelter to position.