Following reports from General Joseph Vuillemin of the French Air Force after a visit to Germany about the strength of the "Luftwaffe", and a memo from André François-Poncet, the French Ambassador to Germany, on 18 August 1938 stating it was quite likely that Adolf Hitler planned to attack Czechoslovakia sometime soon, Bonnet began quite insistent that a joint Anglo-French warning be sent to Berlin against plans to invade Czechoslovakia. On 22 August 1938, Bonnet had Charles Corbin, the French Ambassador in London, press for an explicit British commitment to come to France's side in the event of war breaking out in Central Europe and used the ensuing British refusal as a reason to justify France's lack of intervention in a German-Czechoslovak conflict.