Such a simple invention to cause such a dramatic improvement in mounted soldiers! A stirrup allows for the rider to remain stable even through the fastest gallop and the craziest movement a horse may make; what's more, it allows that rider to carry a much greater weight without falling. And so the next-generation cavalry was born - the heavy-armed Knight. In the February 2017 update the cost of Stirrups was increased from 300 to 360.