In 1443 Donatello was called to Padua to make a colossal equestrian statue in bronze of a condottieri, or mercenary soldier, who had fought for Venice. His name was Erasmo da Narni but he had been nicknamed "Gattamelata" meaning Calico Cat. This work was inspired by the ancient Roman equestrian statue of Marcus Aurelius that Donatello had seen when he was in Rome. Notice how the shapes have been simplified. The tail of the horse is tied so as to repeat the left hoof resting on a cannonball.
This photo shows the horizontal and vertical balance of the sculpture. Notice the spear on the foot and the diagonal unifying axis that runs through the baton.