When the Spanish first arrived in the New World, they held several advantages over the natives they encountered. The most important military advantage was European steel, not the guns that have become so famous. While a few primitive firearms were used to awe the Indians with sound and fury, Spanish swords were so much stronger, sharper and more deadly than the stone and soft-metal weapons of the Indians that battles between them were no contest. Guns were scary but swords did the dirty work. Horses were also a major part of the Spanish military advantage over the Aztecs, Mayans and Incas. The largest South American animals were llamas, and although llama spit can be nasty, it didn't instill fear in the Spanish the way charging, armored horses did to the Indians. And speaking of animals, the Spanish brought war dogs with them. These mastiffs and Great Danes were trained to kill, and they were ferocious. All together, sharp, strong steel, horses, and attack dogs added to guns to give the Spanish a military edge that the Indians could not counter.
The one advantage that the Indians—especially the Aztecs in Mexico—had over the Spanish was numbers. There were millions of Aztecs and only a few hundred Spaniards. How was it then that the Spaniards, even with their steel and guns, could overrun them? The answer lies in a number the Spanish had even more of: microbes. Smallpox, influenza, mumps, measles and a literal host of other diseases decimated the native populations of America. From a pre-Columbus population estimated at 1 million, the native population of Hispaniola (now Haiti and the Dominican Republic) fell to only 500 by 1500.6 Indian society was completely upended by so many deaths. Entire cities lay sick and dying from smallpox and plague; military formations were crushed by disease long before they could attack the Spanish.
However, even amidst so much death and chaos, the diminished Aztecs were able to deal a shattering blow to Cortés and his army of Spaniards and native allies. On 1 July 1 1520, the Spanish army was surrounded on one of the causeways leading from Tenochtitlan to the shore of Lake Texcoco. A night of fierce fighting ensued, and the Spanish were forced to cut their way out, literally over the bodies of Aztec warriors whom they kicked into the shallow waters of the lake. In the end, anywhere from 300-700 Spaniards and up to 4,000 of Cortés's Indian allies were killed; the number of Aztecs killed remains heavily disputed. The night became known in Spain as la noche triste, or Night of Tears, and it was the largest single Spanish defeat during the Conquest. The Spaniards got their revenge, however, as a smallpox plague ravaged the city, allowing Cortes to regroup, gather allies, and conquer the city once and for all the next year. The Aztecs suffered not a single night of tears, but an eternity.
Owing to their numerical inferiority, the conquistadors developed many tactics for defeating the large empires of America. Guile and surprise—also known as treachery—were used to great effect to capture both Moctezuma (a.k.a. Montezuma), the god-king of the Aztecs in Mexico, and Atahaulpa, the last Incan Emperor in Peru. The exact sequence of events that led to the capture of Moctezuma is unclear from the ancient sources, but the story surrounding the capture of Atahaulpa and the slaughter of 2,000 of his soldiers in the square of the Peruvian city of Cajamarca is well-known. Atahaulpa agreed to meet the Spanish invadersin the main square of the city on 16 November 1532, but when he arrived he found no one in sight. Eventually, a Dominican friar appeared with a Bible, and Atahualpa asked to see the book, which the friar had called the "Spanish God." When the Bible did not speak to him, Atahualpa threw it down, giving the Spanish under Francisco Pizarro the excuse—alleged desecration of Christ—they needed to attack. Suddenly, all 168 Spaniards descended on the Incas in the square, their guns belching smoke, flame and noise, and their horses and dogs stampeding into the mass of Indians. Two thousand were killed, and Atahualpa was taken prisoner, later to be executed evenafter filling a large room with gold and silver in a futile effort to win his freedom by paying ransom.7
In Mexico, the Spanish knew that they could not conquer the Aztecs without help, and conveniently for them, the Aztec practice of sacrificing thousands of prisoners of war on their temple steps in celebration of the sun-god did not endear them to their neighbors, who provided the unfortunate human sacrifices. That made it relatively easy for the Spanish to play one group of natives off of another. A major misconception is that Cortés and his small band of less than a thousand Spaniards conquered the huge Aztec empire. Not in the least. What disease had not already wrought was achieved when Toltecs, Mixtecs, Zapotecs and other tribes joined with the Spanish in the thousands. Cortes's gift was figuring out a way to use this native host to conquer the major Aztec city of Tenochtitlan. In Peru, the Incan empire was stronger than the Aztecs and there were fewer tribes to recruit, but there was a civil war in progress when Pizarro arrived, and he used this split in leadership to his own advantage.
The real point to remember is that the arrival of the Europeans with their strange dress, language, habits, foods, and diseases completely shattered Indian society so profoundly that the Spanish were able to exploit the resulting fissures using guile and steel. Yes, the Spanish were militarily more formidable than the Indians, but a healthy, unified, un-traumatized Aztec or Incan society might well have been able to defeat Cortés, Pizarro and the rest.
During the Spanish colonial period the American natives were not the only foe the Spanish faced. Other European powers were eager to gain the riches of the New World for themselves, and Spain was constantly fighting France, England, and the Dutch for control of various parts of the Caribbean and North and South America. To protect the silver shipments from Mexico and South America, the Spanish organized a convoy system: all the military and transport ships would gather in Havana and sail together to Seville, Spain. This was a great system, until 1628 when the Dutchman Piet Hein managed to capture the entire silver fleet near Cuba. Whoops.
But the wealthy Spanish were constantly faced the threat of pirate attacks and foreign incursions. Pirates like Francis Drake and Henry Morgan became national heroes in England for their successes in stealing from the Spanish in the Caribbean. (Henry Morgan stole an entire island—Jamaica—and his reward was to go on to become its Royal Governor. And, of course, to achieve immortality as a brand of rum.) In the American Southwest, the Spanish had to deal with Russian incursions in the 1580s. Spain's navy often sailed all the way up the California coast in the eighteenth century, and a slew of Americans moved south into Texas and New Mexico in the nineteenth century, a migration that precipitated the struggle for Texan independence in the 1830s.