Inca Princesses by Stuart Stirling download in ePub, pdf, iPad
So there was a combination of diplomacy and inducement, coercion, and militarism all wrapped up into one strategic package. One's status in Andean society was often marked by the kinds of gifts that one received from superiors. And some people, of course, got great privileges by collaborating with the state. But the processes by which the Incas came into power were really much longer term than the historical documents would lead us to believe.
In the highlands, most of the population before the Inca peace lived in relatively high elevations, often in communities away from the most productive agricultural lands in the valley. Like the Spanish, the Inca coveted gold, though for different reasons. There are some indications that infant mortality rates decreased substantially under the Incas. By and large, given the chance, people rejected Inca rule at their first opportunity, so we know which side of that equation they came down on. The Incas also had an elaborate food storage system.
So we can think of the expansion of the empire as being largely a product of a couple of generations. The largest storage system was right around Cuzco itself, but if you go out into the provinces, that's where the bulk of the storage in the empire was located. One of the problems with radiocarbon dating is that it's a probabilistic way of measuring the past.
When the Incas developed the empire, they simultaneously used existing structures and innovated. They did this by resettling people in agriculturally productive areas or in areas that were military hotspots.