Complex sentence: The most common crosses were between native mares used by the military or for pulling carriages and Thoroughbred stallions, and in 1914 these types were recognized as "demi-sang" or "half-blood" horses.
Split into simpler sentences: The most common crosses were between native mares used by the military, or those bred for pulling carriages, and Thoroughbred stallions. In 1914 these types were recognized as "demi-sang" or "half-blood" horses.