Extract the answer to the question from the following context. Question: When did the negotiation of the panglong agreement take place? Context: Following World War II, Aung San negotiated the Panglong Agreement with ethnic leaders that guaranteed the independence of Myanmar as a unified state. Aung Zan Wai, Pe Khin, Bo Hmu Aung, Sir Maung Gyi, Dr. Sein Mya Maung, Myoma U Than Kywe were among the negotiators of the historical Panglong Conference negotiated with Bamar leader General Aung San and other ethnic leaders in 1947. In 1947, Aung San became Deputy Chairman of the Executive Council of Myanmar, a transitional government. But in July 1947, political rivals assassinated Aung San and several cabinet members.
Following World War II