Oscarborg’s Austro-Hungarian Whitehead torpedoes carried 100-kg TNT warheads that dated back to 1900 — the last time the fort received a serious upgrade. The torpedoes had been successfully practice-launched more than 200 times, but no one was sure they would actually detonate, due to their age. While the torpedoes’ speed could be set, targeting had to be done via dead reckoning (estimating the distance and speed of the target visually.) A few days before the Nazi invasion, the regular torpedo commander became ill. So the Navy had to call in the nearest local expert, Commander Andreas, who had retired 13 years earlier.