1935: Joins Cavalry Regiment No.17 as officer candidate.
1938: Commissioned as second lieutenant. Participates in the military operations associated with Hitler's annexation of Austria and then Czechoslovakia's Sudetenland.
1941: Assigned to Field Marshal Erwin Rommel's Afrika Korps as first lieutenant. Serves on Korps staff as assistant operations officer. Later promoted to captain. Leads his company into battle with distinction.
June 1942: Earns Iron Cross, Second and First Class for action at battles of El Adem and Trigh Capuzzo.
July 1942: Awarded Knight's Cross for gallantry in first battle of El Alamein while leading battalion in spearhead advance on Egypt under Rommel's command. Severely wounded in that battle, sent home to Germany, and promoted to rank of Major.
Given command of Armored Reconnaissance Training and Replacement Battalion No.24 based at Meiningen.
Recruited into the conspiracy by Colonel Claus von Stauffenberg via a mutual friend, Peter Sauerbuch, and former comrade of Cavalry Regiment No.17.
Hoesslin's planned task is to surround and isolate the fuehrer's Wolf's Lair headquarters with three companies of troops under his command after Stauffenberg
assassinates Hitler. But on July 20, 1944, circumstances beyond his control thwart the plan.
Arrested shortly after July 20, Hoesslin is sentenced to death by the People's Court and executed on October 13, 1944.