province. Four towns had representatives, Middelburg, Zierikzee, Veere
and Flushing. William himself acquired by purchase the marquisate of
Flushing and thus was able to exercise a preponderating influence in the
Provincial Estates, all of whose members were required to be Calvinists
and supporters of the rebel cause.

The investment of Leyden by the Spaniards threatened however, now
that Haarlem had fallen, to isolate South Holland and Zeeland; and
William did not feel himself strong enough to make any serious attempt
to raise the siege. Lewis of Nassau therefore, with the help of French
money, set himself to work with his usual enthusiastic energy to
collect a force in the Rhineland with which to invade the Netherlands
from the east and effect a diversion. At the head of 7000 foot and
3000 horse--half-disciplined troops, partly Huguenot volunteers,
partly German mercenaries--he tried to cross the Meuse above Maestricht
with the intention of effecting a junction with the Prince of Orange.
He was accompanied by John and Henry of Nassau, his brothers, and
Christopher, son of the Elector Palatine. He found his course blocked
by a Spanish force under the command of Sancho d'Avila and Mondragon.
The encounter took place on the heath of Mook (April 14) and ended in
the crushing defeat of the invaders. Lewis and his young brother,
Henry, and Duke Christopher perished, and their army was completely
scattered. The death of his brothers was a great grief to William.
Lewis had for years been his chief support, and the loss of this
dauntless champion was indeed a heavy blow to the cause for which he
had sacrificed his life. He was only thirty-six years of age, while
Henry, the youngest of the Nassaus, to whom the Prince was deeply
attached, was but a youth of twenty-four.

The invasion of Lewis had nevertheless the result of raising the siege