Shakespeare was also brave enough to warn his benefactor about the dangers of a disunited realm in King Lear, which was first produced in 1606 as well.
But if a nation is disunited, the government cannot be sure that the actions of the people will be in the interests of the nation; and it will have to watch, check, and control the people accordingly.
If they cannot disunite them by domestic broils, then they engage their neighbours against them, and make them set on foot some old pretensions, which are never wanting to princes when they have occasion for them.