Original: Otto 's lack of success owed partially to his being the brother of Emil von Zalewski , who on August 17 , 1891 while leading a colonial force against Wehe insurgents in Tanzania was speared to death while his force was annihilated in the battle of Rugarto .
Simplified: His father 's lack of success was partly because he was the brother of Emil von Zalewski , the leader of a colonial force fighting in Tanzania .