But his rival's difficulties were hardly less than his own. Harold was threatened with invasion not only by William but by his brother Tostig, who had taken refuge in Norway and secured the aid of its king, Harald Hardrada. The fleet and army he had gathered lay watching for months along the coast. His one standing force was his body of hus-carls, but their numbers only enabled them to act as the nucleus of an army. On the other hand the Land-fyrd or general levy of fighting-men was a body easy to raise for any single encounter but hard to keep together. To assemble such a force was to bring labour to a standstill. The men gathered under the King's standard were the farmers and ploughmen of their fields. The ships were the fishing-vessels of the coast. In September the task of holding them together became impossible, but their dispersion had hardly taken place when the two clouds which had so long been gathering burst at once upon the realm. A change of wind released the landlocked armament of William; but before changing, the wind which prisoned the Duke brought the host of Tostig and Harald Hardrada to the coast of Yorkshire. The King hastened with his household troops to the north and repulsed the Norwegians in a decisive overthrow at Stamford Bridge, but ere he could hurry back to London the Norman host had crossed the sea and William, who had anchored on the twenty-eighth of September off Pevensey, was ravaging the coast to bring his rival to an engagement. His merciless ravages succeeded in drawing Harold from London to the south; but the King wisely refused to attack with the troops he had hastily summoned to his banner. If he was forced to give battle, he resolved to give it on ground he had himself chosen, and advancing near enough to the coast to check William's ravages he entrenched himself on a hill known afterwards as that of Senlac, a low spur of the Sussex downs near Hastings. His position covered London and drove William to concentrate his forces. With a host subsisting by pillage, to concentrate is to starve; and no alternative was left to the Duke but a decisive victory or ruin. [Sidenote: Battle of Hastings]