Miron Mershon was born in 1917 in Riga into the family of a salesman. In his youth he belonged to the Borokhov-Yugnt leftist Zionist movement. At the age 18 he joined a kibbutz-hakhshara (training commune) near Liepaja, in western Latvia. Mershon's dream was to be a sailor but the naval school rejected him since nationalism prevailed in Latvia of the mid-1930s and the country's fleet gave preference to ethnic Latvians. Nevertheless, Mershon succeeded in being accepted to studying fishing at a school in Liepaja. Following him, two other members of the kibbutz-hakhshara joined the school. Like Mershon, they dreamed of being fishermen in the Land of Israel.
In 1939 Mershon was still waiting for a certificate to enter Palestine, but in the spring of that year he was drafted into the Latvian army. In the summer of 1940, with the annexation of Latvia to the Soviet Union, the Latvian army was re-organized into the Latvian Corps of the Red Army. Overnight Mershon became a Red Army soldier. He was demobilized several days before the German attack on the Soviet Union in June 1941.
With the beginning of the German-Soviet war, Mershon attempted to volunteer for active service, but was rejected since the Soviet authorities regarded the residents of the newly annexed countries as unreliable elements. Mershon and other such volunteers were formed into a quasi-police battalion, which was to fight saboteurs and spies, the notorious "fifth column" of 1939-1941. At the end of June, his battalion was ordered to move to Valka, a town on the Latvian-Estonian border. His battalion continued its police functions in this area. Only in mid-July did it become part of the Red Army (as the1st Latvian Volunteer Regiment), with its members receiving Soviet uniforms. As an experienced soldier (he had served since 1939), Mershon was promoted to be the commander of a company.
In his memoir Mershon stressed that not all of the volunteers of the regiment were admirers of Communism or of the Soviet regime; however, their hatred of the Nazis prevailed. Characteristically, Mershon titled his memoirs "How Fierce Hatred for Nazism Made Me Take Up Arms." The same motivation explained the fact that many of the volunteers were Jewish.
During the following two months Mershon's regiment fought in Estonia. At the end of August, when the Soviet command decided to abandon Tallinn, the regiment was evacuated by sea from the capital of Estonia to Leningrad (now St. Petersburg, Russia). The ship "Ashkhabad," which was transporting Mershon's regiment, was sunk by German bombers. Mershon was picked up by a small Soviet ship and eventually taken to the naval base of Kronshtadt, near Leningrad. Remnants of the 1st Latvian Regiment were included into the 62nd Rifle Regiment. From the end of 1941 to 1943 Captain Mershon, the commander of a heavy mortar company, was engaged in the defense of Leningrad. In January 1943 he was hospitalized because of dystrophy (the German siege of Leningrad caused catastrophic starvation, including among the civilian population of the city). In January 1944, during the Red Army operation to lift the blockade of the city, Mershon was seriously wounded. After his second hospitalization, he was transferred to the Gorokhovetskie training camps in central Russia, where a new Latvian division, the 308th Rifle Division was being formed. In July 1944 the division arrived in Latvia, and Mershon was fighting in his native country. He took part in the recapture of Riga by the Soviets. From November 1944 to March 1945, when he was wounded, he participated in the liquidation of the Wehrmacht's Courland Pocket.
Mershon was awarded two military orders and several medals.
His brother Ilia Mershon, who was born in 1923, volunteered to join the 43rd Guards Latvian Division and was killed in 1942 near Staraia Russa (in northern Russia).
After the war Miron Mershon lived in Riga. In the postwar Soviet Union, he encountered official antisemitism. In 1990 he finally settled in Israel, the country of he had been dreaming of in the 1930s. He lived in Haifa.
 Mershon, Miron. Kak liutaia nenavist k natsizmu zastavila menia vziatsia za oruzhie, Haifa, 2003.