Complex sentence: He was then appointed to SILE then in a Saharan Company Scope of the Foreign Legion (CSPL) until 1955, when he joined the 1st Regiment Stranger (RE) until 1957.
Split into simpler sentences: He was then appointed to SILE then in a Saharan Company Scope of the Foreign Legion (CSPL). In 1955, he joined the 1st Regiment Stranger (RE) until 1957.