In 1915, he gained the men and artillery of the German cruiser which had been scuttled in the Rufiji River delta. The cruiser had a capable crew under commander Max Looff, and its artillery pieces, converted to land use, became the largest standard guns used in the East African Theatre. In March 1916 British forces under General J. C. Smuts and the Belgians under Charles Tombeur launched an offensive with 45,000 men near Tabora. Lettow-Vorbeck used the climate and terrain to his advantage, engaging the British on his terms. British reinforcements forced Lettow-Vorbeck to yield territory. Continuing his resistance, Lettow-Vorbeck fought a crucial battle at Mahiwa in October 1917, where he inflicted 2,700 casualties on the British. Lettow-Vorbeck himself lost 519 men killed, wounded, or missing while also running critically low on ammunition, forcing him to withdraw. The British would proceed to recover their losses and continue to hold an overwhelming advantage in numbers of men. For the "Schutztruppe", this was serious, for there were no reserves with which to replenish their ranks. After news of the battle reached Germany, however, Lettow-Vorbeck was promoted to major-general ("Generalmajor").