While the prince calmly sat before Grave, awaiting the inexorable hour for burghers and garrison to surrender, the great Francis Mendoza, Admiral of Arragon, had been completing the arrangements for his exchange.  A prisoner after the Nieuport battle, he had been assigned by Maurice, as will be recollected, to his cousin, young Lewis Gunther, whose brilliant services as commander of the cavalry had so much contributed to the victory.  The amount of ransom for so eminent a captive could not fail to be large, and accordingly the thrifty Lewis William had congratulated his brother on being able, although so young, thus to repair the fortunes of the family by his military industry to a greater extent than had yet been accomplished by any of the race.  Subsequently, the admiral had been released on parole, the sum of his ransom having been fixed at nearly one hundred thousand Flemish crowns.  By an agreement now made by the States, with consent of the Nassau family, the prisoner was definitely released, on condition of effecting the exchange of all prisoners of the republic, now held in durance by Spain in any part of the world.  This was in lieu of the hundred thousand crowns which were to be put into the impoverished coffers of Lewis Gunther.  It may be imagined, as the hapless prisoners afterwards poured in—­not only from the peninsula, but from more distant regions, whither they had been sent by their cruel taskmasters, some to relate their sufferings in the horrible dungeons of Spain, where they had long been expiating the crime of defending their fatherland, others to relate their experiences as chained galley-slaves in the naval service of their bitterest enemies, many with shorn heads and long beards like Turks, many with crippled limbs, worn out with chains and blows, and the squalor of disease and filth—­that the hatred for Spain and Rome did not glow any less fiercely within the republic, nor the hereditary love for the Nassaus, to whose generosity these poor victims were indebted for their deliverance, become fainter, in consequence of these revelations.  It was at first vehemently disputed by many that the admiral could be exchanged as a prisoner of war, in respect to the manifold murders and other crimes which would seem to authorize his trial and chastisement by the tribunals of the republic.  But it was decided by the States that the sacred aegis of military law must be held to protect even so bloodstained a criminal as he, and his release was accordingly effected.  Not long afterwards he took his departure for Spain, where his reception was not enthusiastic.

From this epoch is to be dated a considerable reform in the laws regulating the exchange of prisoners of war.—­[Grotius]

While Maurice was occupied with the siege of Grave, and thus not only menacing an important position, but spreading, danger and dismay over all Brabant and Flanders, it was necessary for the archduke to detach so large a portion of his armies to observe his indefatigable and scientific enemy, as to much weaken the vigour of the operations before Ostend.  Moreover, the execrable administration of his finances, and the dismal delays and sufferings of that siege; had brought about another mutiny—­on the whole, the most extensive, formidable, and methodical of all that had hitherto occurred in the Spanish armies.