6th of April, 1453. The Last Light of Rome flickers.
On 6 April 1453, Mehmed II’s army arrived before Constantinople and began the formal siege. The Ottomans had spent months preparing and assembling a large force of Turks, other Anatolians, and tributary troops from Bulgaria and Serbia to name but two. As well as that, they brought heavy artillery, including the bombards cast by Orban. These were positioned against the land walls, particularly near the Gate of St. Romanus, where the main effort would fall. This was on top of earlier preparatory work including the gathering of a substantial fleet and the construction of the "Throat Cutter"; the Rumeli Hissar.
Inside the city, Constantine XI Palaiologos commanded a much smaller defending force. Alongside Byzantine troops were Genoese under Giustiniani and other volunteers. In total, the defenders likely numbered fewer than 10,000. The opening phase of the Siege of Constantinople was not defined by immediate assault, but by sustained bombardment and pressure. The walls held but the nature of the threat had changed.
From this point on, it became a matter of endurance.