How did the Ottoman Empire capture Constantinople?

• The Ottoman Empire had been expanding for centuries, and the conquest of Constantinople was a major goal of the Ottomans.
• The Byzantine Empire had been in decline for centuries, and Constantinople was weakened by internal divisions, economic problems, and military defeats.
• Sultan Mehmed II, who was only 21 years old at the time, assembled a massive army and navy to besiege Constantinople.
• The Ottomans used advanced military tactics, including the use of cannons and gunpowder, to breach the city’s walls and overcome its defenses.
• The siege lasted for 53 days, during which time the Ottomans suffered heavy losses but ultimately emerged victorious.
• After the conquest, Mehmed II declared Constantinople the new capital of the Ottoman Empire and renamed it Istanbul.
  See:

1. https://academic.oup.com/ahr/article/119/2/399/44150?login=false