Internationally, de Zúñiga saw Spain's future as part of a strong alliance with the Holy Roman Empire also ruled by the Habsburg family, echoing contemporary "arbitrista" Giovanni Botero, who promoted the concept of a Habsburg family-led hegemony across Europe. De Zúñiga was also influenced by the consequences for Spanish controlled northern Italy should the Austrian branch of the family fail in Germany. De Zúñiga persuaded Philip III to send aid the Emperor in Bohemia in 1619, effectively entering Spain into the Thirty Years War (1618–48). In 1620, he played a key role in the dispatch of the Army of Flanders to aid the Imperial cause, leading to the Spanish victory at the Battle of White Mountain later that year. De Zúñiga was also responsible for key Spanish decisions over the future of the conflict in the Netherlands. The armistice since 1609 had become increasingly tense; whilst de Zúñiga was convinced that a straightforward military victory over the Dutch was unlikely, by 1619 he had concluded that a renewal of hostilities could enable negotiations leading to a treaty more favourable to the Spanish. He was largely responsible for the renewal of the war in 1621; as a consequence, the conflict would stretch on for another 27 years until the peace treaty of 1648.