After the return of John the pressure of the Turks had been evaded by a voluntary subjection, and the Emperor of Constantinople was now a vassal of the Sultan, holding, under his sovereign lord the Turk, the city itself and a few thousand square miles of poverty-stricken territory to the west of the capital. He was compelled to do homage, and to supply a hundred soldiers, captained by one of his sons, whenever the Sultan pleased. There was, however, still a fair revenue from such sources as trade and port duties, and John contrived to excite the envy of his elder son by the luxurious dinners, the choice wines and the pretty dancing-girls, which he could still afford to enjoy. It is enough to say that John IV., in his desolate little Empire, contracted a very severe gout, and Andronicus was not unwilling to run the same risk. When, therefore, John was summoned to join the Sultan’s army in Asia, and Andronicus was once more left in charge, the foolish and egoistical youth made another effort to secure his father’s income. Sultan Murad had left his son Saudgi in charge of his European possessions, and the two princes became close friends. In 1376 the news reached the Sultan that they had disowned their fathers and proclaimed themselves independent sovereigns. The unhappy John was at once suspected of collusion, though the Sultan came in time to realize that John was not at all willing to leave the palace to his son until he was compelled to do so. The conspiracy was soon settled. As the Sultan’s troops approached, the two youths threw themselves in Didymoteichus, but they were compelled to surrender. Murad put out the eyes of Saudgi, and sent Andronicus to his father with orders to inflict the same punishment on him, under pain of war. John directed that his sight should be destroyed by boiling vinegar, and Andronicus was confined in a tower near the Blachernæ palace. His son, a boy of tender years, was punished in the same way, and Maria sadly joined them in the dreary tower.