In 1914 Papen was sent to Washington as a military attaché. While in the United States he helped to arrange for a company in Bridgeport to produce armaments for Germany. However, in 1915 he was forced to leave the country after being accused of attempting to sabotage American armaments production for the Allies.
On his return Papen was sent to Palestine where he served as chief of staff of the 4th Turkish Army. He continued to carry out undercover work and was involved in planning rebellions in Ireland and India and sabotage in the United States. As a result of papers found in Nazareth, a number of Papen's agents were arrested and either imprisoned or executed.
After the First World War Papen joined the Catholic Centre Party (BVP) and in 1921 was elected to the Reichstag. Two years later he purchased a controlling stake in its leading paper, the Germania. Papen immediately sacked the editor and over the next few years attempted to use the newspaper to impose his right-wing views on the party. This plan was unsuccessful and was considered as an outsider in the BVP.
As Papen had only a small political following it came as a great shock when Paul von Hindenburg decided to appoint Papen as chancellor on 31st May, 1932. Papen now decided to gain the support of the Nazi Party by lifting the ban on the Sturm Abteilung (SA) that had been introduced by Heinrich Brüning. This was followed by deposing the Social Democratic Party government in Prussia and aggressive statements about not keeping to the terms of the Versailles Treaty.
Papen's reactionary policies upset Kurt von Schleicher who favoured a coalition of the centre. When Schleicher managed to persuade several government ministers to turn against Papen he resigned from office. Papen now began to plot with Adolf Hitler in an effort to oust Schleicher who was now chancellor of Germany.
With the support of industrial leaders such as Hjalmar Schacht, Gustav Krupp, Alfried Krupp, Fritz Thyssen, Albert Voegler and Emile Kirdorf, Papen persuaded President Paul von Hindenburg to appoint Adolf Hitler as chancellor. Papen, who became vice-chancellor, told Hindenburg that he would be able to prevent Hitler from introducing his more extremist policies.
After the Night of the Long Knives, which included the murder of Kurt von Schleicher, Papen sent a letter to Hitler praising him for "crushing the intended second revolution." Soon afterwards Papen resigned as vice-chancellor and was sent as ambassador to Austria (1934-39) where he plotting successfully for the achievement of Anschluss. This was followed by the post of ambassador to Turkey (1939-44).
Papen retired to Westphalia where he was arrested by Allied forces on 10th April, 1945. He was charged with conspiring to start the Second World War at Nuremberg. He was found not guilty but the German government had him re-arrested and charged him with other offences committed while in Hitler's government.
On 1st May 1947 Papen was judged to be a "major offender" and sentenced to eight years imprisonment. However, like other wealthy supporters of the Nazi regime he was soon forgiven for his crimes and was released in January, 1949.
Papen had his wealth and property returned to him but he did lose his state pension and was deprived of his driving license. In his retirement Papen wrote and published his Memoirs (1952). Franz von Papen died in Obersasbach on 2nd May, 1969.