Pack animal units served in Italy and France during the war, but I have been told that Burma was the only theater of operation where pack animals were used almost exclusively for ground transportation in the combat zone. On the mountain trails and in combat we were limited to the incongruous combination of mule and air transport.
Smith, P. E.
"Pack-Mules In Burma,"
Iowa State University Veterinarian: Vol. 10
, Article 6.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol10/iss2/6