Henry VI, elected King of the Romans since 1169, succeeded his father Frederick and was crowned Holy Roman Emperor by Pope Celestine III in 1191. In his struggle with the Princes to enforce his succession, the tide turned in his favour when the returning crusader King Richard was captured in Austria and only released against an oath of allegiance and an enormous ransom. In 1194 Henry could assert the inheritance claims of his wife Constance by conquering the Kingdom of Sicily. By declaring a new Crusade to reconquer Jerusalem, Henry aimed at an agreement with Pope Celestine III to acknowledge his rule over Sicily. In 1195 the armistice concluded by King Richard ended. Sultan Saladin had already died in 1193 and a conflict over his succession raged in the Ayyubid lands. In view of these favourable developments, the emperor hoped to continue the momentum of the previous campaign. Henry VI decided to take advantage of his father's threat of force against  the Byzantine Empire, affected by the rebellions in Serbia and Bulgaria as well as by Seljuk incursions. Emperor Isaac II Angelos had maintained close ties with the Sicilian ursurper king Tancred of Lecce, he was overthrown in April 1195 by his brother Alexios III Angelos. Henry took the occasion to exact tribute and had a threatening letter sent to the Byzantine emperor in order to finance the planned Crusade. Alexius immediately submitted to the tributary demands and exacted high taxes from his subjects to pay the Crusaders 5,000 pounds of gold. Henry also forged alliances with King Amalric of Cyprus and Prince Leo of Cilicia.
Question: How did Alexius raise the money to submit to tributary demands?
Answer: exacted high taxes