Husen was born in Dar es Salaam, then part of German East Africa, as the son of an askari who held the rank of Effendi. Prior to World War I, he had already learned German and worked as a clerk at a textile factory in Lindi. When war broke out in 1914, both he and his father joined the Schutztruppe and participated in the East African campaign against Allied forces. Husen was wounded in the Battle of Mahiwa in October 1917 and held as a POW by British forces.
After the War, Husen worked as a "boy(servant)" on various cruise ships and worked as a waiter with a Deutsche Ost-Afrika Linie ship in 1925. In 1929, he travelled to Berlin to collect outstanding military pay for himself and his father, but his claims were rejected by the Foreign Office as too late. Husen stayed in Berlin and worked as a waiter. He used his Swahili in language courses for officials and security personnel and as a low paid tutor in university classes, e.g. for the famous scholar, Diedrich Westermann.
He married a Sudeten German woman, Maria Schwandner, on January 27, 1933, three days before Hitler came to power. The couple had a son, Ahmed Adam Mohamed Husen (1933-1938), and a daughter, Annemarie (1936-1939). Husen had another son, Heinz Bodo Husen (1933-1945), from another relationship with a German woman named Lotta Holzkamp - this child was adopted by Schwandner and raised with his half-siblings.
In 1934, Husen applied without success for the "Frontkämpfer-Abzeichen", the front-line veterans' Honour Cross. The German authorities were not willing to bestow the order upon "coloureds" in general, and Paul von Lettow-Vorbeck appeared to have explicitly ruled out the case of Husen in a letter to the foreign office. Husen nevertheless wore the badge and an askari uniform which he probably bought from a military supplies dealer during his participation in rallies of the German neo-colonialist movement, which sought to reclaim Germany's lost colonies. .
Whether he had received or lost German citizenship at all is not clear. It was common practice in Weimar Germany to provide migrants from the former German colonies with a passport carrying an endorsement "Deutscher Schutzbefohlener“ (German Protegee) which didn't give them full citizenship. After Hitler's rise to power, black Germans from the former colonies were often deemed to be nationals of the state that had succeeded Germany as the relevant colonial power under the Treaty of Versailles. As in the case of Hans Massaquoi, there was no level of discrimination against black Germans comparable to the systematic hatred the Jewish minority faced.