 In the meantime , British warships bombarded Dar es Salaam and destroyed the German wireless station there . By this time , Königsberg 's engines required a thorough overhaul , and Looff needed to find a secluded area where the work could be completed . He settled on the Rufiji Delta , which had recently been surveyed by the survey ship Möwe . On 3 September 1914 at high tide , Königsberg passed over the bar at the mouth of the Rufiji and slowly made her way up the river . Coast watchers were stationed at the mouth of the river and telegraph lines were run to ensure the Germans would not be surprised by British ships searching for them . Zimmer , who was sending small coastal steamers to resupply Königsberg , observed a British cruiser — Pegasus — patrolling the coast for two weeks . He deduced that the ship would likely have to coal at Zanzibar on Sundays , and so Looff decided to attack the ship in port before he began his overhaul . He considered the action justified , since Britain had rejected a German proposal to keep central Africa neutral according to the Congo Act of 1885 . 
