Robert Merriman, the son of a lumberjack, was born in the United States in 1908. While studying economics at University of Nevada he spent two years in the Reserve Officers' Training Corps because it paid seven and a half dollars a month. He also worked as a ranch hand, cement worker and pulp feeder to help finance his studies.
After completing his studies Merriman began teaching at University of California. While in California he became active in left-wing politics and supported the San Francisco General Strike. Merriman also won the Newton Booth Travelling Fellowship. This enabled him to study agricultural problems in different countries in Europe.
In 1937 Merriman joined the Abraham Lincoln Battalion, a unit that volunteered to fight for the Popular Front government during the Spanish Civil War. He joined the other International Brigades at Albacete and as he spent two years in the Reserve Officers' Training Corps at the University of Nevada, he was recruited to train recently arrived volunteers from America.
Working under James Harris, a former sergeant in the United States Army, Merriman taught the men how to fieldstrip rifles and machine-guns. He also organized a series of lectures on scouting, fortifications and signaling.
His wife, Marion Merriman, joined him in Spain and became the only woman to become a full member of Abraham Lincoln Battalion. She served as an administrative officer until being sent home in November 1937 to begin a speaking tour of the United States.
After failing to take Madrid by frontal assault General Francisco Franco gave orders for the road that linked the city to the rest of Republican Spain to be cut. A Nationalist force of 40,000 men, including men from the Army of Africa, crossed the Jarama River on 11th February, 1937.
General José Miaja sent three International Brigades to the Jarama Valley to block the advance. Led by Merriman, the 373 members of the brigade moved into the trenches on 23rd February. When the were ordered over the top they were backed by a pair of tanks from the Soviet Union. On the first day 20 men were killed and nearly 60 were wounded.
On 27th February 1937, Colonel Vladimir Copic, the Yugoslav commander of the Fifteenth Brigade, ordered Merriman and his men to attack the Nationalist forces at Jarama. As soon as he left the trenches Merriman was shot in the shoulder, cracking the bone in five places. Of the 263 men who went into action that day, only 150 survived. Merriman was now replaced by Oliver Law as battalion commander. It was the first time in American history that an integrated military force was led by an African-American officer.
When Merriman recovered from his wounds he was appointed as brigade chief of staff of the Mackenzie-Papineau Battalion. The next major action involving the International Brigades 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. Merriman ordered the men to take the church. In the first assault involving 22 men, only two survived. When Merriman ordered a second attack, Hans 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, Nelson and Amlie received head wounds and amongst the dead were Wallace Burton, Henry Eaton and Samuel Levinger.
In March 1938 Merriman returned to the Aragón front. Milton Wolff was now battalion commander and John Gates was battalion commissar. Later that month Robert Merriman was reported missing with David Doran while fighting at Gandesa. The following year Edwin Rolfe wrote in The Lincoln Battalion that they were killed by crossfire while on the road to Corbera on 2nd April, 1938.