In the lead up to Trooper‘s vanishing, British Intelligence learned the Germans were planning an assault on the islands, and, in response, the submarine, commanded by Lt. John S. Wraith, traveled to the Aegean Sea for what, from the outside, appeared to be a simple patrol. Trooper arrived on September 30, dropped off her passengers, and went about conducting her usual war patrols until October 5, when she was ordered to keep watch of the waters between Naxos and Icaria, as the British had, once again, received word of an enemy attack, this time on Leros.