Complex sentence: The Commandos secured the camp for the mission's air force, that arrived the night of the 18th and was composed of six Mirage F1 and four Jaguar fighter-bombers and a battery of low altitude (anti aircraft) Crotale missiles.
Split into simpler sentences: The Commandos secured the camp for the mission's air force. The air force arrived the night of the 18th and was composed of six Mirage F1, four Jaguar fighter-bombers, and a battery of low altitude (anti aircraft) Crotale missiles.