Military

"I hate the Army."

- Francis "I love the Goddamned Army!"

- Francis

The Military is essentially, the unified military forces (or what remains of them) of the United States of America, where both Left 4 Dead and Left 4 Dead 2 take place. As a background entity, they play a part in attempting to contain the Infection, as well as scattering improvised military way-points, outposts, and rescue areas along with military-grade weaponry for any living Survivors to defend themselves from the Infected. Unfortunately for the Military, many of them have succumbed to the Infection themselves, and appear as part of the huge army of Common Infected.

Involvement with containing The Infection
The Military was working alongside CEDA in an attempt to fight the Green Flu epidemic and stop its spread. As CEDA failed to contain the virus, the Military eventually took over CEDA's responsibilities as the Infection spread throughout the country. Originally the Military's strategy was to evacuate and rescue as many people as possible but once that became less feasible they began containing and bombing overrun areas. The Military had separated Carriers (people who were infected by the Green Flu, but did not show any symptoms) from non-Infected Survivors (people who had not encountered the Infected) and reportedly shot them. This is demonstrated in The Park when in front of the sealed trailer piles of uninfected corpses can be seen with bullet wounds, which Nick remarks on. Eventually, as the situation got out of hand, even non-Infected people were shot by the Military.

At the initial outbreak, CEDA outlawed civilian gun use (which many Survivors obviously ignored). However, when the military took over these rules were overturned, and civilians were encouraged to arm themselves for their own safety. CEDA also appears to have been less aggressive in dealing with unruly Survivors, which may be one of the many reasons they failed. The military has taken a much more violent stance. Several signs throughout Left 4 Dead 2 state that deadly force is authorized.

Outposts
Riverside: Overrun by day Fourteen or earlier.

Millhaven: Overrun by day Seventeen.

New Orleans Bridge: Overrun and evacuated by day Twenty-Four (presumably).

Safe Zone Echo: Status unknown.

Ships outside New Orleans: Status unknown.

Military Rescue
The Military are still active in rescuing living Survivors, though possibly due to thinning numbers, cannot afford to station personnel at every rescue area to greet and co-ordinate any Survivors. Nevertheless, they usually leave means of contact, generally via radio for any living Survivors to communicate to them. As the Infected are unable to speak any human language anymore, or use technology for that matter, the Military can be assured any attempt at communications will be genuine.

Places in which the Military will actively send Rescue Vehicles:
 * A military C-130 Hercules plane flies over the city of Newburg at the beginning of Dead Air. The plane lands at the ruins of Metro International Airport to refuel the plane however the "co-pilot" is killed by the infected and the plane awaits for Survivors to help refuel the plane since the pilot most likely refuses to leave the safety of the plane.
 * Farmhouse Finale, Blood Harvest. The Military set up a radio along with ammunition and weapons in a farmhouse. When contacted, they will send out a M93 Fox Armored Personnel Carrier to pick up the Survivors communicating with them - if they are still alive.
 * The Bridge, The Parish. The Military have started to evacuate Survivors onto large cruise ships out at sea, having abandoned the mainland. When contacted, the last helicopter is already ready to leave, but will delay their flight along with bombing run if the remaining Survivors on the other side of the bridge can make it to them. The helicopter is a CH-53 Sea Stallion, noticeably equipped for Carriers - Survivors who retain their humanity and are generally immune from the effects, but may still be infected with the Green Flu and able to pass it to others who might not display such a resistance.

Military Presence
Throughout the Left 4 Dead series, the Military have also shown their presence via the use of posters and signboards displaying instructions and warnings. The use of deadly force by the Military is repeatedly emphasized showing their seriousness compared to CEDA. Abandoned vehicles and military weapons have also been left behind as areas are overrun by the Infected.