Which country was first to use horses?

It's impossible to definitively say which country was the *first* to use horses.

Here's why:

* Domestication is a gradual process: The transition from wild horses to domesticated horses likely happened over a long period, perhaps thousands of years, and wasn't a single event in one location.

* Early evidence is sparse: Archaeological evidence of early horse use is limited and often open to interpretation.

* Different regions, different uses: Early horse use may have developed independently in different parts of the world for different purposes (e.g., hunting, transportation, warfare).

Some of the earliest known evidence of horse domestication comes from:

* The Pontic-Caspian Steppe: This region, stretching across parts of modern-day Ukraine, Russia, and Kazakhstan, shows evidence of horse domestication as early as 4000 BCE.

* Central Asia: Evidence suggests horse use and domestication in Central Asia around the same period.

* China: The earliest known evidence of horse domestication in China dates back to about 3500 BCE.

While pinpointing the exact origin is difficult, it's clear that horse domestication was a significant development that occurred independently in several regions of the world around the same time.