From 1928 to 1931 he served as instructor of organization and mobilization at the War School of the Royal Italian Army, then as chief instructor of organization and mobilization from 1931 to 1933 and finally as commandant of the Nunziatella Military School of Naples.

[2][3][4][5][6][7] During the early part of World War II Chatrian, as a French speaker, was attached to the Italian Armistice Commission with France.

In February 1942 he assumed command of the LI Special Brigade "Lecce", stationed in Crete for garrison duty, being promoted to brigadier general in April 1942.

[2][8] On 5 September 1943, after the Allied landings in Calabria, nineteen soldiers of the 76th Coastal Battalion, stationed in Acquappesa and part of the 227th Division, deserted together to return to their homes (all hailed from Calabria); five were recaptured after a few hours, and Chatrian gave order to summarily execute them by firing squad.

In 1945 Chatrian was indicted for these killings but absolved, further investigation being prevented by his parliamentary immunity, although in 1968 – after his death – the Italian Court of Audit ruled that his order had been "a mistake" and "gravely illegal".