Knud Clauson Kass is one of the Danish pilots who volunteer for the Finnish Winter War in 1939/40. He is also a veteran of the Finnish Civil War of 1918.
Knud Alexander Carl Christian Collis Frederik von Clauson Kaas in born on 3 June 1894 in Stenstrup, Funen. He is the son of Second Lieutenant Gustav Adolph Frederik Clauson von Kaas and Selina Hviid. 
Volunteers for the Finnish Civil War 1918
In 1918 Knud Clauson Kaas is engaged in The Finnish Civil War 1918 as part of the White Finnish Air Force. He had not trained as pilot at the time, and was thus observer. He returns to Denmark after the war. 
Trained as army pilot
Knud Clauson Kaas is originally trained as pilot in the Army Air Corps. He gets his wings as early as in 1926 (pilot's certificate 70/26) at holds the rank of Løjtnant (Lieutenant) at the outbreak of war 
Volunteers for the Winter War
In 1940, when Finland enters the Winter War with Russia, Clauson Kaas volunteers for the Finnish Air Force – at the age of 45 he is oldest pilot in the air force. Following basic training he is engaged in ferrying Gloster Gladiators from Sweden to Finland. He is accompanied by Mogens Fensbo, who had been in Finland for about a month at the time.
The two pilots are then transferred to Lentolaivue 28 (Flying Squadron 28) on Morane-Saulniers engaged in the air defences of the South-Western cities. As the Russians advance and the situation becomes desperate the squadron takes part in offensive operations as well.
In March 1940, the Moscow Peace Treaty is signed and the war ends. Knud Clauson Kaas leaves Helsinki on 5 April 1940 and returns to Copenhagen on 7 April 1940 – two days before the German occupation. 
- Stenstrup parish record, Clauson Kaas, 1941
- Clauson Kaas, 1940
- Ancker, 2001, Clauson Kaas, 1943
- Clauson Kaas, 1940, Ritaranta, 1979