When Nazi Germany attacked Norway in April 1940, setting off war, Lt. Cdr. Horve was the commander of HNoMS "Draug". During the night of 9 April, "Draug" was patrolling and watching shipping in the Karmsund. At about 0200hrs, Horve was notified that Oslofjord Fortress was engaging an unknown enemy force in the Oslofjord, leading to the crew being ordered to full combat stations. At 0400hrs, an unknown ship, flying no national flag, was observed sailing northwards through the Karmsund. The ship refused to stop after both flares and warning shots had been fired and "Draug" had to give chase and capture the vessel. After leading the unknown ship into Haugesund, its identity was found to be the 7,624 ton German vessel "Main". The two ships left Haugesund at about 0900hrs, but soon came under attack from a Luftwaffe bomber around off the Norwegian coast. The bombs, aimed at the "Main", missed but the German captain immediately scuttled his vessel and ordered his crew to abandon ship.