Complex sentence: The hotel served the needs of air defense during the second world war, and immediately after the cessation of the war, it served as the headquarters of the international monitoring group overseeing finnish compliance with peace treaty obligations.
Split into simpler sentences: The hotel served the needs of air defense during the Second World War. Immediately after the cessation of the war, Hotelli Torni served as the headquarters of the international monitoring group overseeing finnish compliance with peace treaty obligations.