U.S. Military

The United States Military is an omnibus term for the unified military forces (or what remains of them) of the United States of America: the country that provides the setting for The Walking Dead and The Walking Dead (TV Series). As a background entity, they play a part in attempting to contain the Infection, as well as scattering improvised military waypoints, outposts, and rescue areas. Unfortunately for the Military, many of its members have succumbed to the Infection and so appear (in their camoflage fatigues) as part of the army of Walkers.

Involvement with containing the Epidemic
The Military was working alongside FEMA in an attempt to fight and stop the zombie epidemic from spreading. Originally, the Military's strategy was to evacuate and rescue as many people as possible as seen at the hospital where Rick Grimes woke up, but once that became less feasible, it is evident that a political decision was taken to suspend the rescue and shoot the infected walkers on sight (as seen at the beginning of TS-19). So far, only the United States Army was shown to have been deployed to hault the infection. However, fighter jets were heard during the chaotic evacuation of Harrison Memorial Hospital on Day five; indicating that the United States Air Force was running strike missions against the army of walkers.

Military Bases/Outposts

 * King County, Georgia - The military set up a base near the hospital and assisted with the evacuation of the medical staff and patients to take them to the city of Atlanta. During the evacuation, the infected individuals were everywhere and despite the military's efforts to killing everyone and destroying/bombing certain areas, they pull out and abandon the outpost as seen by Rick Grimes.
 * Atlanta, Georgia - The military focused most of its efforts and attempts to keep the city of Atlanta protected from the infected walkers. Barricades and sandbags were set up all throughout the streets of Atlanta armed with personnel and tanks and other equipment. Helicopters were flying above patrolling the city as well as bring in evacuees however, the walkers made their way there and overpowered the military. It seems that some soldiers fought to the very end before being killed by the horde of walkers. Eventually, the military gave up on protecting the city and ordered a napalm strike on the streets to try and kill the undead however, the bombing had little effect as once again seen by Rick, the walkers were still roaming the streets. However, Rick's sighting of a Huey Helicopter flying over Atlanta may indicate that the military is still in action; in the state of Georgia at least.
 * The CDC - One of the more critical buildings in the city of Atlanta was the Center for Disease Control where scientists and doctors tried to find a cure to the infection. The military knew that civilians would try and make their way there looking for refuge so they set up a checkpoint outside and tried to protect the building as much as possible. However, one again, the walkers triumph over the military as numerous corpses both of the undead and military are seen by Rick and his group of survivors.
 * Unnamed High School - the high school was converted into a FEMA evacuation center and command post. The military units here was trying to protect the shelter and escort refugees to a safe location however, once again they were overrun and along with infected FEMA officials, military soldiers can also be seen wondering the school grounds aimlessly as walkers.
 * Fort Benning - According to Shane, the best chance of survival is the military base there. Shane says that if the base were still operating, they would be heavily armed and away from the hotzone of infection from the city. It is unknown if the military are still there or if they abandoned it. At a bar, Rick along with Glenn and Hershel are found by two strangers, Tony and Dave. Dave tells Rick that Fort Benning was overrun by Walkers but he may have been lying. The Huey Helicopter that Rick saw over Atlanta has a range of around 300 miles. Fort Benning, being 125 miles from Atlanta, would logicaly still be in operation by that performance.

Equipment
Only United States Army and Marine Corps equipment and persons have been shown so far. The UH-1 Huey helicopter was shown many times either abandoned, bombing walkers, or running evac flights. Humvees were shown parked in several areas around Atlanta. Rick took shelter inside an M1A2 Abrams Tank when he first arrived in Atlanta. USMC Bradley IFVs were stationed outside of the CDC. M2 Browning Fifty calliber machine guns were posted on sandbag barriers. Army soldiers were shown carrying M4A1 assault rifles. US Marine CH-53E Super Stallion helicopters were also seen firebombing Atlanta.

US Army is seen using MOPP Chemical protection gear Fort benning May have responded sending most of its troops to atlanta to handle the infection.

it is unknown what part the Us military plays in season 3

Trivia

 * The only known and credited soldier is Private Gaines (played by Mike Senior) in the episode, TS-19.
 * The Tank soldier seen in Days Gone Bye was portrayed by Brian Stretch and was a walker at the time.