The war between the Spanish Empire and the Ottoman Empire is one of the great global conflicts of the early modern era, seeing direct conflict in Europe, Africa, and Asia, with the Americas contributing a critical amount of wealth to the conflict. It started a hot minute or three after the Spanish and their Portuguese allies drove the last of the Muslim kingdoms out of the Iberian Peninsula. After the better part of eight centuries of enduring the initial Muslim invasion and the long Reconquista to retake their lands, the Iberians had no intention of allowing another invasion to happen. The Portuguese quickly expanded into the open seas to create a new economic empire covering Southern Africa and Southern Asia and the Spanish walked into the nearest Muslim kingdoms in North Africa with blood in their eyes. Those kingdoms asked the Ottomans for help, and it was on like Donkey Kong.
Their allies in the Ethiopian Empire and the Holy Roman Empire fought sporadic hot and economic wars in Eastern Europe and the Horn of Africa, while the Portuguese and Spanish sailed all over the world to fight the Ottomans and their allies and proxies wherever they found them. Barbary Corsairs. Arabian Raiders. Indian Sultanates. The Sulu Sultanate of the Philippines. They claimed the Americas, found vast wealth there that helped fund their global conflicts, and the sun never set on the Spanish Empire centuries before it never set on the British Empire. The Ottomans maintained effective control of the Eastern Mediterranean despite constant Iberian pressure, but the Iberians fought the Ottomans and their various allies from Africa to Europe to India.
And everywhere the Spanish and Portuguese armadas and armies went, so did their treasure hunters, priests, and settlers looking for new opportunities. It was a mass migration of millions of Spaniards into the new worlds. At least five million Iberians left the peninsula over the next four centuries. That was a statistically significant amount of the total population of Iberia, and it remade the New World, especially after Old World diseases wiped out millions of the native populations in the New World, and millions of slaves from Africa were imported to replace them. Expanding Hispanic populations created the dominant cultures throughout South and Middle America, and as we all know, much of Southern and Southeastern North America also came under their sway.
The Iberian Mass Migration effectively remade the world in their image, and is one of the most consequential mass migrations in known history.