But fate was unkind to him. The discovery of America diverted Castilian energy from Aragonese objects, and death stepped in and made grim sport of all his marriage jugglery. Before he died, beaten and broken-hearted, he knew that the little realm of his fathers, instead of using the strength of others for its aims, would itself be used for objects which concerned it not. But though he failed his plan was a masterly one. Treaties, he knew, were rarely binding, for the age was faithless, and he himself never kept an oath an hour longer than suited him; but mutual interests by kinship might hold sovereigns together against a common opponent. So, one after the other, from their earliest youth, the children of Ferdinand and Isabel were made political counters in their father's great marriage league. The eldest daughter, Isabel, was married to the heir of Portugal, and every haven into which French galleys might shelter in their passage from the Mediterranean to the Bay of Biscay was at Ferdinand's bidding. The only son, John, was married to the daughter of Maximilian, King of the Romans, and (from 1493) Emperor, whose interest also it was to check the French advance towards north Italy and his own dominions. The second daughter, Juana, was married to the Emperor's son, Philip, sovereign, in right of his mother, of the rich inheritance of Burgundy, Flanders, Holland, and the Franche Comté, and heir to Austria and the Empire, who from Flanders might be trusted to watch the French on their northern and eastern borders; and the youngest of Ferdinand's daughters, Katharine, was destined almost from her birth to secure the alliance of England, the rival of France in the Channel, and the opponent of its aggrandisement towards the north.