His act was declared unconstitutional by Prime Minister Hubert Pierlot and his cabinet, who presently moved to London to form a government-in-exile, while Leopold and his family were placed under house arrest. In 1944, they were moved to Germany and then Austria, before being liberated by the Americans, but banned for some years from returning to Belgium, where his brother Prince Charles had been declared regent. Leopold's eventual return to his homeland in 1950 nearly caused a civil war, and under pressure from the government, he abdicated in favour of his son, Prince Baudouin, in July 1951.