Serving with the U.S. Army Special Forces, Törni was involved in operations conducted by MACV-SOG when the helicopter he was on crashed under unclear circumstances.

After attending business school and serving with the Civil Guard, Törni entered military service in 1938, joining Jaeger Battalion 4 stationed at Kiviniemi; when the Winter War began in November 1939, his enlistment was extended and his unit confronted invading Soviet troops at Rautu.

[8] After the Winter War, in June 1941, Törni went to Vienna, Austria for seven weeks of training with the Waffen-SS, and returned to Finland in July; as a Finnish officer, the Germans recognized him as an Untersturmführer.

[10] Koivisto served in a reconnaissance company under Törni's command during the Battle of Ilomantsi, the final Finnish-Soviet engagement of the Continuation War, during July and August 1944.

[14] The training was prematurely ended in March, but as Törni could not secure transportation to Finland, he joined a German unit to fight Soviet troops near Schwerin, Germany.

[19] In 1949, Törni, accompanied by his wartime executive officer Holger Pitkänen, traveled to Sweden, crossing the border from Tornio to Haparanda (Haaparanta), where many inhabitants are ethnic Finns.

From Haparanda, Törni traveled by railroad to Stockholm where he stayed with Baroness von Essen, who harbored many fugitive Finnish officers following the war.

Now a political refugee,[21] Törni traveled to New York City where he was helped by the Finnish-American community living in Brooklyn's Sunset Park "Finntown".

In 1953, Törni was granted a residence permit through an Act of Congress[22] that was shepherded by the law firm of "Wild Bill" Donovan, former head of the Office of Strategic Services.

From 1958 to 1962, he served in the 10th Special Forces Group in West Germany at Bad Tölz, from where he was second-in-command of a search and recovery mission high in the Zagros Mountains of Iran, which gained him a notable reputation.

In an episode of The Big Picture released in 1962 and composed of footage filmed in 1959, Thorne is shown as a lieutenant with the 10th Special Forces Group in the United States Army.

[26] During a fierce attack on the CIDG camp in Tịnh Biên, he received two Purple Hearts and a Bronze Star Medal for valor during the battle.

[1] On 18 October 1965, as part of the operation Shining Brass, Thorne was supervising the first clandestine mission to locate Viet Cong turnaround points along the Ho Chi Minh trail and destroy them with airstrikes.

[1] Formally identified in 2003, his remains were buried on 26 June 2003 at Arlington National Cemetery, along with the RVNAF casualties of the mission recovered at the crash site.

Major Thorne was operations officer responsible for launching a small, combined reconnaissance patrol on an extremely hazardous mission into a suspected Viet Cong stronghold.

Due to the extreme hazards attending this mission, including weather and enemy action, Major Thorne volunteered to accompany submission aircraft during the introduction of the patrol in place of the assigned individual.

Major Thorne's actions were in keeping with the highest traditions of the military service, and reflect great credit upon himself and the United States Army.

[49] Furthermore, Finnish historian and later Minister of Defence (2015–2019) Jussi Niinistö of the right-wing populist Finns Party argued that Törni's training was actually motivated by patriotism towards his native country, and accused Pohjonen and Silvennoinen of stirring up hatred in order to promote sales of their book while disregarding "the fact that in Finland there was a genuine fear that Russia would occupy Finland.