Name the date and invention that made horses a viable military option.?

Stirrups were the invention that made horses a viable military option. They were invented in the 3rd century BC in northern India and China, and were introduced to Europe by the 6th century AD. Stirrups allowed riders to stay on their horses more securely, which enabled them to use their hands more effectively for fighting. This made horses much more effective in warfare, as riders could now use both hands to wield weapons and shields, and could also charge at opponents with greater force.