On September 2, 1946, Jawaharlal Nehru was sworn in as vice-president of the Interim Government of India, the first cabinet of Indians to hold executive power under British rule. He effectively led the government, while the Viceroy, Lord Wavell, remained head of state.
The arrangement came out of the Cabinet Mission plan, which had failed to keep India united. The Muslim League refused at first and joined only in October, entering the government with the stated aim of blocking it from inside, which turned the cabinet into a coalition that could not act as one. Liaquat Ali Khan took the finance portfolio. He used it against Congress.
What made the interim government significant was scope rather than power. It controlled defence, external affairs and finance, which meant Indians were running the machinery of the state for the first time since 1858. It also meant the argument over partition moved out of principle and into administration: who gets which department, which province, which seat at the table.
It lasted eleven months. The League wanted parity and a veto, Congress wanted a united India, and the provinces were already breaking into communal violence. Lord Mountbatten replaced Wavell as Viceroy in March 1947. Independence came that August. Partition came with it.