context: In 1665, the Mughal Emperor Aurangzeb decided to take action on the Arakanese marauders and launched the Mughal conquest of Chittagong. He also wanted to avenge for his brother Shah Shuja who was killed in exile by the Arakanese king. The Mughal viceroy of Bengal first lured the Portuguese mercenaries in the service of King Sanda Thudhamma guarding the Chittagong region to defect by giving them fiefs. Then the Mughal fleet took Sandwip in late 1665. In January 1666, a Mughal force of 6500 men and 288 boats took Chittagong after a 36-hours' siege. They subsequently took as far south as Ramu. Arakan had lost the Chittagong province which it had held since 1459. Arakan would not recover from the loss of Chittagong, and went into rapid decline. Central authority collapsed in the late 17th century. Sanda Wizaya  briefly revived the kingdom. He went to war with Tripura, and raided Sandwip, Prome and Malun. But after his death, Arakan reverted to chaos where king after king was murdered and central authority barely existed. It was easily overrun by the Konbaung armies in 1784-1785.
question: What started first: Mughal conquest of Chittagong or Mughal fleet took Sandwip?
answer: Mughal conquest of Chittagong