Who invented a device that allowed farmers to replace the strength of oxen with speed horses?

The invention you're thinking of is likely the horse-drawn plow. This device didn't directly replace oxen with horses, but it adapted the existing plow technology to be used with the speed and agility of horses.

While there isn't a single inventor credited with its creation, the horse-drawn plow evolved over time, with advancements being made by various cultures across different periods.

However, it's important to note that:

* Oxen and horses were used together: Farmers often used both oxen and horses for different tasks. Oxen were more powerful for heavy plowing, while horses were quicker for lighter tasks or smaller fields.

* The invention was gradual: The development of the horse-drawn plow was a gradual process with contributions from many individuals and civilizations.

Therefore, attributing the invention to a single person is challenging, as it was more of a progression of technology.