Complex sentence: On 1 January 1945, by decree of General Charles de Gaulle based on the untried accusations of collaboration, the company was expropriated from Louis Renault posthumously and on 16 January 1945 it was formally nationalised as "Régie Nationale des Usines Renault".
Split into simpler sentences: On 1 January 1945, by de Gaulle's decree, the company was posthumously expropriated from Louis Renault. On 16 January 1945 it was formally nationalised as "Régie Nationale des Usines Renault".