On 17 September 1939, he was nominated president of Poland by retiring President Ignacy Mościcki. On the same day, Poland was invaded by the Soviet Union and he took the train from Rome to Paris to take on his new role. His appointment was published in the Official Journal, Monitor Polski, on 25 September 1939. His appointment was blackballed by the French Third Republic and also opposed by Władysław Sikorski. After the capitulation of France, he emigrated to New York travelling via Lisbon.