On 1 July 1945 Bowes was promoted
Squadron Leader, this was confirmed later. He moved to Rinteln in Germany in late 1945 as officer commanding
Special Investigation Branch within British Air Forces of Occupation, and commenced investigations on the ground, travelling to Soviet occupied Poland and Czechoslovakia, travelling into Berlin and even flying to
Moscow to interrogate a man he wanted who would not be released by the Soviet
NKVD secret police due to warrants for mass murder in Russia. Bowes and his deputy
Frank McKenna headed the 15-man investigation detachment of the
Special Investigation Branch of the
Royal Air Force Police given the assignment to tracking down the killers of the 50 officers. The investigation started seventeen months after the alleged crimes had been committed, making it a
cold case. Worse, according to an account of the investigation, the perpetrators "belonged to a body, the Secret State Police or Gestapo, which held and exercised every facility to provide its members with false identities and forged identification papers immediately they were ordered to go on the run at the moment of national surrender." Bowes is recorded as an extremely effective interrogator, and an officer leading armed raids on the hiding places of desperate war criminals. The team from the RAF relentlessly tracked down, arrested, and interrogated the alleged war criminals responsible for the murders. Work by Bowes,
Frank McKenna and the team saw a number of those guilty of the murders tried for their crimes. Others were dead or in Soviet custody facing capital charges for other crimes . Bowes' investigations continued through 1947 and he maintained active links with war crimes investigators in Moscow in the hope of securing the extradition of the man he had interrogated, but in October 1947 the Russians confirmed that he had died. ==Post-war==