Speaking strictly of horses....what good are they gonna do in the Andes? Especially war chariots, that makes no sense at all. If the Inca are anticipating a war with a foreign interloper, a prepared Inca state would be hellish to invade due the litany of mountain passes that render horses useless. The Inca'd find great value in using horses to expand down the Rio de La Plata and Parana regions, but other than that, I'm not seeing the strategic value in the short to medium term at all, not even for transportation. On the topic of agriculture, horses are a different story entirely but with respect to food production the Andes did pretty damn well even without Old World domesticates. Introducing them shortly after the worst of the plagues hit could really help the population rebound. Plentiful food, lots of kids, etc.
Regarding Horses, The Conquest, and Difference In Tactics (Because Horses And Different Evolution In Warfare):
"Without horses, the evolution of complex European economies and trading networks would have been unthinkable. Most significantly, the horse transformed the art of war. From the earliest horse-drawn chariots of the Hittite empire, to the bareback cavalrymen of Attila the Hun, the warhorse has become synonymous with Eurasian military success.
Spanish horses were instrumental in the conquest of the New World. Neither the Aztec nor the Inca had ever seen humans riding animals before; the psychological impact of mounted troops was tremendous.
Hernan De Soto, comrade of Pizarro, famously rode his horse right into the Inca Emperor's throne room. Eyewitnesses later recalled:
"The captain advanced so close that the horse's nostrils stirred the fringe on the Inca's forehead. But the Inca remained still, he never moved."
[...]
On the morning of November 16, 1532, a surprise charge of just 37 Spanish horses, concealed in the Inca town of Cajamarca, unleashed an orgy of bloodshed. Europeans had known for centuries that foot soldiers stood a good chance against cavalry if they stood firm and repelled the outnumbered mounted troops. But the Inca had no experience of this, nor could they have read about others' experiences, since they were geographically isolated and had no written records from which to learn. Instead, they panicked and tried to flee, allowing the outnumbered conquistadors to run through them with great speed and efficiency." ~
Guns Germs & Steel
"Francisco Pizarro too followed a code different from that of his opponents. He invited Atahualpa, the Inca ruler, to the Spanish camp in Cajamarca, in today’s northern Peru, and then ordered an attack against the mostly unarmed Inca escorts. The Incas stripped temples of their gold wall-plates and ornaments to pay the ransom for Atahualpa’s release. The Spaniards melted down 11 tonnes of gold objects, and then, after a hasty “trial”, killed him.
Here too they faced resistance for almost a year. Indeed, the fierce topography of the Andes allowed the rump Inca mini-state of Vilcabamba to survive until 1572. But by the 1540s, Spain had conquered the main population centres of Central America and western South America. The Portuguese would penetrate Brazil far more slowly.
The Spaniards won because they had better tactics—Aztecs in battle tried to capture, not kill, their opponents—and technology. Horses, mastiffs and guns terrified Aztecs and Incas armed with slings, stonetipped clubs and spears (though Inca archers did better)." ~
The Conquest
Regarding Animals And The Resources Provided:
-Cows: Large and strong, produce a great deal of meat, milk, and leather. Dung makes good fuel and fertilizer. Mature in two to three years, docile herd animals and eat plentiful grass.
-Sheep: Mature very quickly and ready to breed qhen they a 1 & 1/2 years old. Can weight between 80 and 400 pounds and produce milk, sheepskin, lamb, and dung makes good fuel and fertilizer.
-Goat: Can survive in colder and rockier climates than cows, can eat just about anything. Provides meat, wool, and enough milk that one or two could keep a family fed for a year.
-Pigs: Very easy to look after as they're omnivorse, provides plenty of meat and reproduces in litters.
-Llama: Very temperamental, can't carry a persons weight because lacking in strength. Provides wool, meat, dung and hide.
Having more resources allows greater growth and expansion, which ostensibly also allows for more innovation. Also, I can't imagine the mountains proving all that challenging, its not like they could only go either on horse or foot and were not allowed to switch whenever convenient, or create settlements as bases, or build bridges or anything. The Incas were using convoys of llamas to ferry silver they mined so there had to be a way for such animals to get around their territory.
