In 894 Stylianos Zaoutzes, leading minister of Leo VI, convinced the emperor to move the Bulgarian market from Constantinople to Thessaloniki. That move affected not only private interests but also the international commercial importance of Bulgaria and the principle of Byzantine–Bulgarian trade, regulated with the Treaty of 716 and later agreements on the most favoured nation basis. The transfer of the Bulgarian market to Thessaloniki cut short the direct access to goods from the east, which under the new circumstances the Bulgarians would have to buy through middlemen, who were close associates of Stylianos Zaoutzes. In Thessaloniki the Bulgarians were also forced to pay higher tariffs to sell their goods, enriching Zaoutzes' cronies.

The ousting of the merchants from Constantinople was a heavy blow for Bulgarian economic interests. The merchants complained to Simeon I, who in turn raised the issue to Leo VI, but the appeal was left unanswered. Simeon, who according to the Byzantine chroniclers was seeking a pretext to declare war and to implement his plans to seize the Byzantine throne, attacked,provoking what has sometimes been called (inappropriately) the first commercial war in Europe.