Short answers, pulled from the story.
The Blue Division was a unit of Spanish volunteers in the German Wehrmacht that formed after the German invasion of the Soviet Union began on the 22nd of June 1941. Recruitment started on the 27th of June 1941 and 18,373 men had volunteered by the 2nd of July 1941.
Francisco Franco sympathized with fascist ideology especially its anti-communism stance which motivated his decision to support Germany after the Fall of France in 1940. He met Adolf Hitler on the 24th of October 1940 at Hendaye but failed to gain promises for colonial territories before allowing volunteers to fight against the Soviet Union.
The division suffered 22,700 casualties while inflicting 49,300 casualties against the Red Army during their service period. Through rotation as many as 45,000 Spanish soldiers served on the Eastern Front over time.
On the 3rd of November 1943 the Spanish government ordered all troops to return to Spain ending the main division's service. Fresh volunteers formed new pro-German Spanish units collectively called the Blue Legion and some returned home on the 21st of March 1944.
Hundreds of Blue Division prisoners of war were held by Soviet authorities after the conflict ended because Francoist Spain and the Soviet Union did not have diplomatic relations. 286 men remained in captivity until the 2nd of April 1954 when they finally returned to Spain aboard a vessel supplied by the International Red Cross.