Dohna was drafted into the "Wehrmacht" at the start of World War II and served as a Rittmeister throughout the German invasion of Poland and later the Soviet Union. On 18 January 1943 he was one of the last to be evacuated from Stalingrad, carrying personal letters and the awards of Friedrich Paulus. From January 1944 he served with the LXXV Army Corps in Italy. In March 1944, a U.S. Army commando group of 15 men had landed near La Spezia to blow up railway tunnels as part of Operation Ginny II but were captured by German and Italian troops. Even though these men were wearing US army uniforms (and were therefore POWs), Dohna was ordered to sign the execution orders. However, Dohna refused to do so as this would have violated the 1929 Geneva Convention on Prisoners of War (thereby constituting a war crime); he was dismissed from the Wehrmacht for this insubordination. General Anton Dostler, who signed the execution order, was tried for this war crime after hostilities ended. Dostler was subsequently convicted, sentenced to death and executed by firing squad.