The two Marines assigned to her pushed, pulled and sweet-talked her up the steep, twisting trail on the eastern side of the Sierra Nevada.
"C'mon, girl, you can make it," Lance Cpl. Chad Campbell whispered in her ear.
"Only one more hill," promised Lance Cpl. Cameron Cross as he shoved Annie's muscular hindquarters.
The red-hued donkey snorted, nibbled on grass and let loose that distinctive braying, which begins with a loud nasal inhalation and concludes with an even louder blast of deep-throated protest.
She also dropped green, foul-smelling clumps, which the Marines carefully sidestepped.
On the rocky, uneven path, Annie never stumbled. A good donkey, Marines say, knows three steps ahead where it wants to walk.
For Campbell and Cross, the day with Annie could be a preview of days to come. The two may soon deploy to Afghanistan, where donkeys and mules have been the preferred mode of military transport for centuries -- and remain so.
With the U.S. shifting its focus from the deserts of Iraq to the mountains of Central Asia, this course on pack animals at the Marine Corps Mountain Warfare Training Center has become critical to the new mission.
Opened in 1951 to train troops for Korea, the center -- with its administrative buildings, barracks, corrals and an enormous tent for visiting troops -- is set on 47,000 acres of the Humboldt-Toiyabe National Forest, where serrated peaks above 10,000 feet are the perfect terrain to teach high-altitude combat skills.
Five donkeys, 24 mules and five sergeant trainers are stationed at the center for the course, which is given eight times a year to Marines, Army soldiers, Navy SEALs and some foreign troops.
Humvees and even helicopters are of limited use in Afghanistan's mountains. There are few roads and the air is thin. But a 1,000-pound mule or 400-pound donkey can easily carry a load one-third its weight -- or more, if necessary.
The weapons of war have changed, but the basics of handling donkeys and mules -- like the sawbuck saddle and packs on Annie -- are not much different from how they were in the time of Genghis Khan.
"It's a very primitive way to carry very modern weapons," said Sgt. Joe Neal, one of the instructors. "But it works."
On the first day of the 12-day course, Campbell, Cross and 40 other junior Marines, all from Camp Pendleton, listened intently at the corral in Pickel Meadows as instructors spoke of battles won with the help of four-footed allies.
One of the Marine Corps' most fabled heroes, Sgt. Maj. Daniel Daly, earned his second Medal of Honor for leading pack animals into combat against Haitian bandits in 1915.
Assigned one of the older, scruffier mules, two of the Marines later insisted the animal must have deployed with Daly.
The students learned to pack machine guns, mortars, grenades, Javelin missiles and M-16 ammunition, as well as food, water and medical supplies -- all needed to carry the fight to the enemy.
"The Taliban are born mountain men, they can move faster in that terrain than we can," said Staff Sgt. Tyler McDaniel, an Iraq war veteran who is now the lead instructor for the course. "The pack animals are a force multiplier. They make sure we can get enough gear and men to the fight."