Fevers and horrible malaria, bred by the blazing sun of the equator out of those pestilential jungles, poisoned the atmosphere.  His handful of troops, amounting to not much more than a hundred men to each of his ships, might melt away before his eyes.  Nevertheless, although it was impossible for him to carry the place by regular approach, he would not abandon the hope of reducing it by famine.  During four months long, accordingly, he kept every avenue by land or sea securely invested.  In August, however, the Spanish viceroy of India, Don Alphonso de Castro, made his appearance on the scene.  Coming from Goa with a splendid fleet, numbering fourteen great galleons, four galleys, and sixteen smaller vessels, manned by three thousand seven hundred Portuguese and other Europeans, and an equal number of native troops, he had at first directed his course towards Atchen, on the north-west point of Sumatra.  Here, with the magnificent arrogance which Spanish and Portuguese viceroys were accustomed to manifest towards the natives of either India, he summoned the king to surrender his strongholds, to assist in constructing a fortress for the use of his conquerors, to deliver up all the Netherlanders within his domains, and to pay the expenses of the expedition which had thus been sent to chastise him.  But the King of Atchen had not sent ambassadors into the camp of Prince Maurice before the city of Grave in vain.  He had learned that there were other white skins besides the Spaniards at the antipodes, and that the republic whose achievements in arts and arms were conspicuous trophies of Western civilization, was not, as it had been represented to him, a mere nest of pirates.  He had learned to prefer an alliance with Holland to slavery under Spain.  Moreover, he had Dutch engineers and architects in his service, and a well-constructed system of Dutch fortifications around his capital.  To the summons to surrender himself and his allies he returned a defiant answer.  The viceroy ordered an attack upon the city.  One fort was taken.  From before the next he was repulsed with great loss.  The Sumatrans had derived more profit from intercourse with Europeans than the inhabitants of Johore or the Moluccas had done.  De Castro abandoned the siege.  He had received intelligence of the dangerous situation of Malacca, and moved down upon the place with his whole fleet.  Admiral Matelieff, apprised by scouts of his approach, behaved with the readiness and coolness of a veteran campaigner.  Before De Castro could arrive in the roadstead of Malacca, he had withdrawn all his troops from their positions, got all his artillery reshipped, and was standing out in the straits, awaiting the enemy.