Complex sentence: General de Gaulle himself was only informed by Churchill on 4 June 1944 that the Allies planned to land in France on 6 June and until then the Free French leaders had no idea when and where Operation Overlord was due to take place.
Split into simpler sentences: General de Gaulle himself was only informed by Churchill on 4 June 1944 that the Allies planned to land in France on 6 June. Until then the Free French leaders had no idea when and where Operation Overlord was due to take place.