Complex sentence: He was posted to a Czechoslovak training unit in Agde on the coast of Languedoc, where he applied to transfer to join the Czechoslovak Air Force group in the French "Armée de l'Air".
Split into simpler sentences: He was posted to a Czechoslovak training unit in Agde on the coast of Languedoc. There he applied to transfer to join the Czechoslovak Air Force group in the French "Armée de l'Air".