Prior to the popularity of minced or ground beef like Salisbury steak in the United States, similar foods already existed in the culinary tradition of Europe. The Apicius cookbook, a collection of ancient Roman recipes that may date to the early 4th century, details a preparation of beef called isicia omentata; served as a baked patty in which minced or chopped beef is mixed with pine kernels, black and green peppercorns, and white wine, isicia omentata may be the earliest precursor to the hamburger. In the 12th century, the nomadic Mongols carried food made of several varieties of milk (kumis) and meat (horse or camel). During the life of their leader Genghis Khan (1167–1227), the Mongol army occupied the western portions of the modern-day nations of Russia, Ukraine, and Kazakhstan, forming the so-called Golden Horde. This cavalry dominated army was fast moving and sometimes unable to stop for a meal, so they often ate while riding. They wrapped a few slices of meat under their saddles so it would crumble under pressure and motion and be cooked by heat and friction. This recipe for minced meat spread throughout the Mongol Empire until its split in the 1240s. It was common for Mongol armies to follow different groups of animals (such as herds of horses or oxen or flocks of sheep) that provided the necessary protein for the warriors’ diets. Marco Polo also recorded descriptions of the culinary customs of the Mongol warriors, indicating that the flesh of a single pony could provide one day’s sustenance for 100 warriors.