[1] Klán was engaged to Václava—daughter of the popular Czech romance novelist Vlasta Javořická—in 1939, shortly before the dissolution of the First Czechoslovak Republic and the establishment of the German-administered Protectorate of Bohemia and Moravia.

[3][4] He became a fighter ace after achieving an additional four aerial victories during the Battle of France, for which he would be invested into the Legion of Honour at the rank of Chevalier (knight) and decorated with the Croix de Guerre.

[1] After the Fall of France, Klán made his way to the United Kingdom via French Algeria and volunteered with Czech and Slovak expatriates serving the Royal Air Force, briefly commanding No.

[1][5] He later moved to the USSR where he was made deputy commander of the Soviet-backed 1st Czechoslovak Fighter Air Regiment, which provided combat aviation support to insurgent forces during the Slovak National uprising.

[2] As John Kent, Klán worked for a government services firm and, then, for Piper Aircraft as a sales manager variously posted to the company's offices in Brazil, Argentina, and Switzerland.