You propose to bind a distant kingdom to your league, not by conquest, nor by subjection, but as a companion. This is the second of the three methods by which commonwealths extend their power, and I have judged it the soundest: to provide yourself with allies or companions, taking heed, however, to retain in your own hands the chief command, the seat of government, and the titular supremacy. The Romans followed it and reached a power that had no limit. The Spartans and Athenians held other states in direct subjection, and came to ruin from no other cause than that they had acquired a dominion greater than they could maintain.
But I would caution you to look closely at the nature of the bond you are creating. A prince ought to take care never to make an alliance with one more powerful than himself for the purpose of attacking others, unless necessity compels him; because if he conquers, you are at his discretion. And the Venetians, who for many years sought no dominion beyond what served their commerce, were held in veneration and chosen to arbitrate the quarrels of others; yet when they reached for empire, the states entered into an alliance against them and in one day wrested from them the provinces they had obtained with so much labor and expense. What matters here is whether this new companion strengthens the league without placing it at the discretion of another, or whether it merely adds a name to a bond that cannot be maintained.