Seriously to hold the West India Islands required, first, a powerful seaport, which the French had; second, the control of the sea.

For the latter it was necessary, not to multiply detachments in the islands, but to destroy the enemy's navy, which may be accurately called the army in the field.

The islands were but rich towns; and not more than one or two fortified towns, or posts, were needed.
It may safely be said that the principle which led to D'Estaing's action was not, to say the least, unqualifiedly correct; for it led him wrong.

In the case of Yorktown, the principle as stated by Ramatuelle is not the _justifying_ reason of De Grasse's conduct, though it likely enough was the _real_ reason.

What justified De Grasse was that, the event depending upon the unshaken control of the sea, for a short time only, he already had it by his greater numbers.
Had the numbers been equal, loyalty to the military duty of the hour must have forced him to fight, to stop the attempt which the English admiral would certainly have made.