The treaty restored the status quo ante bellum, and the terms of the treaty were favourable both to Spain and England. For Spain the treaty secured her position as a leading power in the world. Spain's upgrading of the convoy system had allowed it to defend its treasure fleets and retain its New World colonies. English support for the Dutch rebellion against the Spanish king, the original cause of the war, had ended. The Spanish would then concentrate their efforts on the Dutch in order to bring them to their knees with a knockout blow. A complete abandonment of the Dutch cause however was not promised in the treaty. The English held cautionary towns in Holland on the other hand were not surrendered despite Spanish demands. The sieges of Ostend and Sluis were allowed to continue until the end of those respective campaigns. The Dutch by 1607 had in fact prevailed - the Spanish did not deliver their knock out blow they had hoped for; the Twelve Years' Truce formally recognized the independence of the Republic.