In late December, the cruiser was assigned to the blockade of German East Africa, and sailed for Zanzibar on 9 January 1915. On arrival, "Pioneer" was ordered to help contain the German cruiser in the Rufiji River and prevent German supply ships from arriving. "Königsberg" was scuttled on 12 July following shelling by two monitors, although "Pioneer" remained in the region until 31 August, when she sailed to Simon's Town in South Africa for a six-week refit. "Pioneer" returned to uneventful patrols of German East Africa on 22 October, and continued until early February 1916, when the Admiralty instructed the ship to return to Australia. However, before she could leave, demands by General Jan Smuts for more Admiralty involvement in the East African Campaign saw "Pioneer" return to patrols on 24 February. On 30 July, the cruiser fired 100 4-inch shells during the bombardment of Dar-es-Salaam.