Gabriel made an alliance with the Hajdúsirregular troops stationing along the borders of Transylvania and Royal Hungaryand laid claim to Transylvania against the elderly prince, Sigismund Rákóczi in February 1608. Rákóczi abdicated and the Diet of Transylvania elected Gabriel prince without resistance. Both the Sublime Porte and the Habsburg ruler Matthias II acknowledged Gabriel's election. He ignored the privileges of the Transylvanian Saxons and captured their wealthiest town, Szeben (now Sibiu in Romania), provoking an uprising in 1610. His attempts to expand his authority over the Ottoman vassal Wallachia and his negotiations with Matthias II outraged the Ottoman Sultan Ahmed I. The Sultan decided to replace Gabriel with an exiled Transylvanian nobleman, Gabriel Bethlen, and sent troops to invade the principality in August 1613. Transylvania was unable to resist and the Diet dethroned Gabriel. He was murdered by Hajdú assassins.