So dry he was for sway wi’ th’ King of Naples
To give him annual tribute, do him homage,
Subject his coronet to his crown and bend
The dukedom, yet unbowed – alas, poor Milan! –
To most ignoble stooping.

– William Shakespeare

The Tempest, Act 1, Scene 2. Prospero says that his brother Antonio was so hungry for power that he allied himself with the King of Naples Alonso, agreeing to pay him an annual tribute and be subservient to him. So he put the dukedom of Milan under the ignoble control of Milan.