german warmblood may refer generally to any of the various warmblood horses of germany, or more specifically to a warmblood registered with the nationwide german horse breeding society (zfdp). beneath the umbrella term "german warmblood" are several regional variations on a singular standard; individual german warmblood types are not necessarily considered "breeds", because they have an open stud book and freely exchange genetic material between each other, with other warmblood types, with anglo-arabians, and with breeds like the thoroughbred, arabian, and trakehner. (the trakehner, while a warmblood horse from germany, has a closed stud book and thus, like the thoroughbred and arabian, is considered a "true" breed.)