ke out between Geoffrey,
Count of Anjou, and Henry (1048), and William came to his suzerain's
assistance. Alencon, one of the chief border fortresses between
Normandy and Maine, which had received an Angevin garrison, was
captured by the duke. The inhabitants had taunted him with his birth,
and William, who had dealt leniently with the rebels after
Val-es-Dunes, took a cruel revenge. Soon afterward Domfront, another
important border fortress, fell into his hands.

In 1051 William visited England. Two years later he married Matilda,
daughter of Baldwin, Earl of Flanders, and a descendant of Alfred. The
marriage had been forbidden by a council at Rheims as uncanonical, and
was opposed by Lanfranc, Prior of Bec. This produced a quarrel between
Lanfranc and William, who ravaged the lands of the abbey and ordered
the banishment of its prior. Lanfranc, however, soon came to terms
with the duke, and engaged to obtain a dispensation from Rome, which,
however, was not granted till 1059.

Strengthened by this alliance with Flanders, William showed himself
more than a match for all his enemies. Henry, who had hitherto been
for the most part friendly, now turned against him. After the
suppression of some isolated revolts, William was threatened in 1054
by a great confederacy. His dominions were invaded by the forces of
the French king, in combination with those of Geoffrey of Anjou,
Theobald of Blois, and others. William remained at first on the
defensive; then, falling suddenly on one of the French armies at
Mortemer, in the north-eastern corner of his duchy, he cut it to
pieces. This blow put an end to the war; Henry made peace (1055), and
William took the opportunity of extending his dominions in a southerly
direction. He built fresh fortresses and exacted homage from Count
Geoffrey of Mayenne.

In 1058 Henry and Count Geoffrey made a final effort to crush their
dangerous neighbor; but the effort failed, like those which preceded
it. William again allowed the allies to enter and ravage his
territory; but, while the French army was crossing the Dive at
Varaville, he attacked and completely destroyed their rear-guard,
which was cut off from the van by the advancing tide. Henry again made
peace, and soon afterward died (1060). The death of Geoffrey of Anjou
in the same year relieved William of his most formidable rival for the
possession of Maine. Herbert Wake-Dog, the lawful ruler of that
territory, who had been dispossessed b