The Front, because of strong popular support as France was reeling from the impact of the Great Depression, won the 1936 election.

The Party supported the Soviet Union's tactical treaty with Germany in order to direct German aggression away from the USSR and toward the United Kingdom and France.

Following the German invasion of the Soviet Union in June 1941, the French Communist Party openly declared it would violently resist the German occupation; even before this, the Communist Party organized a demonstration of thousands of students and workers against the occupation on 11 November 1940, and in May 1941 organized a strike of 100,000 miners in the Nord and Pas-de-Calais departments.

During this time, articles written by and ghostwritten for Thorez appeared frequently in the party's underground newspaper, Humanité Clandestine.

In his absence, the affairs of the PCF and of the Francs-Tireurs et Partisans, the party's resistance movement, in France were organised by his second in command, Jacques Duclos.

When General Charles de Gaulle's Free French Forces liberated France in 1944, Thorez received a pardon.

After the Liberation, Thorez was ordered by Stalin to lead the PCF immediately after the Second World War to a non-revolutionary road to power.

By 1947 a combination of the emerging Cold War between the United States and the Soviet Union and growing social conflicts in France, linked to the increasing gap between wages and prices, put the three party union (SFIO, PCF and MRP) under heavy pressure, culminating in the May 1947 crisis.

Prime Minister Paul Ramadier received threats from the United States that the presence of Communist ministers in the government would have consequences, such as the blocking of U.S. aid from the coming Marshall Plan, or worse: "I told Ramadier," Jefferson Caffery, then U.S. ambassador to France, wrote in his diary, "no Communists in gov.

I knew that Ramadier was cooking up something bad, but never did I think he'd go this far…[4]In 1950, at the height of his popularity among party members, Thorez suffered a stroke and remained in the Soviet Union for medical care until 1953.

Although his health had deteriorated, Thorez remained party leader until shortly before his death in 1964 on a Black Sea cruise.