The departments of Nord and Pas‐de‐Calais were home to 300,000 Polish immigrants who had arrived throughout the 1930s to fill the shortage of labour created by the high French death toll in the First World War, as well as to escape the repressive régime back in Poland. Over 40,000 Poles worked in the coal‐mining industry and like the majority of their workmates, the Polish miners were affected by the lack of food.

These Polish immigrants were politically divided between, on the one hand, members of the CGT and the sympathisers of the Communist party, and on the other, activists in the Polish organisations that were supported by the Polish authorities and members of catholic religious organisations. The left wing was organised around the Polish speaking section of the French Communist Party and the veterans of the Dabrowski Brigade, who had fought in the Spanish civil war.

In 1936, the Polish groupings in the CGT had 80,000 members, of which 35,000 were in the 56 Polish sections in the Pas‐de‐Calais. Moreover, the majority of catholic Poles in the mines supported the union organisation led by the Communists out of workplace solidarity, seeing this as the best way to defend their common interests. This same solidarity led them to solidly support the strikes.

In January 1941, when the mining companies lengthened the miners’ working day by half an hour, miners in some pits left their posts and refused to work during this extra time; in the mine at l’Escarpelle, the strike call was given by Polish miners. When the mining companies alerted the [Axis] authorities, the ensuing arrests of 53 miners included a number of Polish Communists. During the strike of May–June 1941, Jan Rutkowski and Rudolf Larysz were both members of the central strike committee with many Poles also working on the local strike committees.^42^

(Source.)