After the 7th century AD, Abydos became a major seaport. Maslama ibn Abd al-Malik, during his campaign against Constantinople, crossed over into Thrace at Abydos in July 717. The office of "archon" at Abydos was restored in the late 8th century and endured until the early 9th century. In 801, Empress Irene reduced commercial tariffs collected at Abydos. Emperor Nikephoros I, Irene's successor, introduced a tax on slaves purchased beyond the city. The city later also became part of the theme of the Aegean Sea and was the seat of a "tourmarches".