Duke Charles had terrible forces at command. A body of mercenary troops, known as the Black Band, had been used by George of Saxony for the repression of Friesland in 1514, and since then had been seeking employment wherever they could find it. At the same time, one of the conquered Frieslanders, known as Long Peter, had turned to piracy as an effective way of revenging himself on Holland. Proclaiming himself 'King of the Sea', he seized every ship that came in his way, showing no mercy to Hollanders and holding all others to ransom. In May 1517, the Duke, violating a truce not yet expired, renewed hostilities. The Black Band, some of whom had strayed as far as Rouen in quest of fighting, flocked back. At the end of June 3000 of them crossed the Zuider Zee in Long Peter's ships and disembarked suddenly at Medemblik, in North Holland. The town was quickly set on fire, and everything destroyed except the citadel; the fleet carrying back the first spoils. Then they marched southwards, burning what they list; and happy were those whose offer of ransom was accepted, to escape with plunder only. There was no fixed plan. The murderous horde wandered along, turning to right or left as fancy suggested. After burning five country towns, they appeared at Alcmar, the chief town of North Holland, into which the most precious possessions of the neighbourhood had been hurriedly conveyed. By a heavy payment, the burghers purchased immunity from the flames; but for eight days the town was given up to the lust and ferocity of an uncontrolled soldiery, from whose senseless destruction it took thirty years to recover. Egmond, with its great abbey, was pillaged; and then it was Haarlem's turn to suffer. But by this time resistance had been organized. Troops had been called back from garrison work in Friesland, and a strong line drawn in front of Haarlem. Headed off, the Black Band turned suddenly away. Passing Amsterdam and Culemborg, it penetrated down into South Holland, whence it would be easy to pass back into Gueldres. Asperen was its next prey. Three times the citizens beat off the cruel foe: a few more to man their walls, and they might have driven him right away, to overwhelm others less fortunate and less brave.