The long-standing disputes as to fishing rights in the narrow seas and at Spitsbergen, and as to trading spheres in the East Indian Archipelago, remained unsettled; and in the unfortunate and ill-considered war, which broke out at this time between England and France, the sympathies of the States were with the latter.

Already those close relations between the French and the Dutch, which for the next decade were to be one of the dominating factors in determining the final issue of the Thirty Years' War, were by the diplomatic efforts of Richelieu and of Aerssens being firmly established.

France advanced to the States a large subsidy by the aid of which the stadholder was enabled to take the field at the head of a really fine army and to give to the world a brilliant display of his military abilities.

Throughout his stadholderate the persistent aim which Frederick Henry held before himself was never aggression with a view to conquest, but the creation of a scientific frontier, covered by strong fortresses, within which the flat lands behind the defensive lines of the great rivers could feel reasonably secure against sudden attack.

It was with this object that in 1629 he determined to lay siege to the town of Hertogenbosch.