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David-Weill became a partner in the Paris office of the family's bank in 1927, when its Chairman was Raymond Philippe.
Along with Lazard Frères minority partner, André Meyer, Pierre David-Weill and his family fled the German occupation of France during World War II to the safety of the United States. There, he took charge of the firm's office in New York City where he remained until the liberation of France by Allied Forces in 1944. On his return to Paris, he left André Meyer in charge of American operations and along with Felix Rohatyn, they expanded Lazard Frères business to make it a leading Euro-American investment bank.
David-Weill married Berthe Haardt in 1932. They had a son, Michel David-Weill (born 1932) and a daughter, Eliane David-Weill born in 1935.
Pierre David-Weill died in 1975. Despite converting to Catholicism in 1965, he is interred with his wife in the Jewish section of the Cimetière du Montparnasse in the Montparnasse Quarter of Paris.
- Cohen, William D. (2007). The Last Tycoons: The Secret History of Lazard Freres & Co. Knopf Doubleday Publishing Group. p. 52-53. ISBN 978-0385521772.