 In 1911, Bästlein finished his training as a mechanic and joined the Socialist Workers Youth Party ("Sozialistischen Arbeiterjugend"), where he met his future wife, the seamstress Johanna Elisabeth Hermine Berta Zenk, daughter of Wilhelmine (née Schröder) and Albert Zenk, a working-class family and Social Democrats.The following year, Bästlein joined the metal workers' union and the SPD and from 1913 till 1915, he went to work at different armaments factories, at which point he became a soldier and went to fight in France on the western front in 1916.In 1917, he began to write articles about the revolutionary developments then taking place in Russia.