Hans Amlie was born in the United States. He worked as a mining engineer and was a member of the Socialist Party of America.
On the outbreak of the Spanish Civil War Amlie helped form the Eugene V. Debs Column. Only 25 members of the party joined and disgusted at the response Amlie joined the American Communist Party.
On his arrival in Spain Amlie joined the other International Brigades at Albacete. He later became a member of the Abraham Lincoln Battalion.
Amlie took part in the battle of Jarama River in February, 1937 and was injured at Mosquito Ridge in July, when his commanding officer, Oliver Law was killed.
In August 1937 the American forces were reorganized. Steve Nelson was promoted to brigade commissar and Robert Merriman became brigade chief of staff. Amlie, who had now recovered from his wounds suffered at Mosquito Ridge, became commander of the Lincoln-Washington Battalion.
The next major action involving the Lincoln-Washington Battalion took place during the Aragón offensive at the end of August 1937. The campaign began with an attack on the town of Quinto. This involved dangerous street fighting against snipers that were within the walls of the local church. After two days the Americans were able to clear the town of Nationalist forces. This included the capture of nearly a thousand prisoners.
The Lincoln-Washington Battalion then headed towards the fortified town of Belchite. Once again the Americans had to endure sniper fire. Robert Merriman ordered the men to take the church. In the first assault involving 22 men, only two survived. When Merriman ordered a second attack, Amlie at first refused saying the task of taking the church was impossible. He help Amlie, Steve Nelson led a diversionary attack. This enabled the Lincoln-Washington Battalion to enter the town. The Americans suffered heavy casualties, Amlie, Nelson and Merryman all received head wounds.