In 1948, when war broke out between the newly declared State of Israel and the neighbouring Arab states, Koestler was accredited by several newspapers, American, British and French, and travelled to Israel. Mamaine Paget went with him. They arrived in Israel on 4 June and stayed there until October. Later that year they decided to leave the UK for a while and move to France. News that his long-pending application for British nationality had been granted reached him in France in late December; early in 1949 he returned to London to swear the oath of allegiance to the British Crown.