The siege of Trebizond was the successful siege of the city of Trebizond, capital of the Empire of Trebizond, by the Ottomans under Sultan Mehmed II, which ended on 15 August 1461. The siege culminated a lengthy campaign on the Ottoman side, which involved coordinated but independent manoeuvres by a large army and navy. The Trapezuntine defenders had relied on a network of alliances, which would provide them with support and a workforce when the Ottomans began their siege. Still, it failed when Emperor David Megas Komnenos most needed it.