Born in 1880, Knief began training to be a primary school teacher in 1901, joining the Social Democratic Party of Germany (SPD) a few years later.
Drafted by the Imperial German Army to fight in the First World War in August 1914, he was discharged after suffering a nervous breakdown on the Western Front.
A staunch opponent of the Burgfriedenspolitik supported by a majority of the SPD's parliamentary membership, he welcomed Karl Liebknecht's rejection of war credits in the Reichstag on 2 December 1914.
After the Bremen revolt was put down by the Army and Freikorps Caspari, he briefly went into hiding together with other escaping revolutionaries (among them Heinrich Vogeler) in Worpswede.
On 9 March he was designated a deputy of the Communist Party in the Bremer National Assembly, but died from the complications of no less than five operations for appendicitis on 6 April.