rate 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. A force of 24,000 infantry and 4000
cavalry were gathered together for the enterprise. It was composed of
many nationalities, like all the armies commanded by Maurice and
Frederick Henry, but was admirably disciplined and devoted to its
commander. Four English, three Scottish and four French regiments, all
choice troops, raised by permission of their sovereigns for the service
of the States, formed the backbone of the force. On April 30 the town
was invested.

Hertogenbosch, or Bois-le-duc, was strongly fortified, and so surrounded
by marshy ground, intersected by a number of small streams, that the
only way of approach for a besieging force was a single causeway
defended by the forts of St Isabella and St Anthony. The garrison
consisted of 8000 men, and the governor, Grobendonc, was an experienced
and resolute soldier.

The stadholder began by surrounding the town with a double line of
circumvallation. The marshes were crossed by dykes, and two streams were
dammed so as to fill a broad deep moat round the lines and flood the
country outside. Other lines, three miles long, connected the investing
lines with the village of Crevecceur on the Meuse, Frederick Henry's
base of supplies, which were brought by water from Holland. These works
completed, approaches were at once opened against the forts of St
Anthony and St Isabella, the task being entrusted to the English and
French troops. The court of Brussels now began to take serious measures
for relieving the town. At first regarding _Bolduc la pucelle_ as
impregnable, they had been pleased to hear that the prince had committed
himself to an enterprise certain to be a dismal failure. Then came the
news of the circumvallation, and with it alarm. The Count de Berg was
therefore ordered (June 17) at the head of an army of 30,000 foot and
7000 horse to advance into North Brabant and raise the siege. But the
stadholder was prepared and ceaselessly on his guard; and the Spanish
general, after several vain attempts, found the Dutch lines
unassailable. With the view of compelling F