A Flare is a pyrotechnic device used to illuminate environments at night, for signalling, and as a countermeasure against infrared-guided weapons.
Throughout all games in the ArmA series, flares can be deployed through a variety of methods. Notable examples include Star Parachute Flares which are fired from underbarrel grenade launchers like the American M203 or Russian GP-25, which slowly drop back to earth with a parachute extending the amount of time it illuminates its surroundings.
In low-light situations or during poor weather, they can be used to illuminate areas if friendly troops do not have night vision equipment or to signal friendly aircraft for a pick up. However if carelessly or incorrectly deployed at the wrong moment, then a lit flare will quickly give away the user's position.
Countermeasure-based flares on the other hand, are launched by aircraft as a way of warding off incoming IR-guided missiles. The effectiveness of such flares against IR-guided weapons varies on the aircraft's heading and elevation. They can be either highly effective or completely useless if the aircraft remains stationary, since the missile will continue to home in onto the largest heat source regardless of the flares.
Because countermeasure flares are completely useless against radar-guided weapons, they are almost always deployed in conjunction with chaff dispensers as well.
ArmA: Cold War Assault
UGL flares were available in pale white, bright green, pale red and flat yellow colours. They generally provided illumination for up to 30 seconds after being launched.
With the rarity of infantry night vision equipment and complete lack of NV-capable sights, flares were highly important for nighttime operations, with every American and Soviet infantry squad usually having at least one or two members carrying flares for illumination in low-light conditions.
It should also be noted that aircraft in Cold War Assault do not have access to flare launchers, due to the relative short range of infantry MANPADS like the 9K32 or the Stinger, as well as the general lack of air-to-air missiles on fixed-wing jets.
M203/EGLM launchers used their own specific type of flare shells, while weapons that were fitted with the Russian GP-25; usually found on Russian-made rifles such as the AK-107 or AK-74, used their own respective flare grenades instead. The U.S. Army's M32 multiple-shot grenade launcher was also capable of loading cylinders that could fire up to six flares at once (though at the cost of them being unable to carry a rifle).
Flares in ArmA 2 are also available in white, red, green and yellow colour varieties. They lasted anywhere from 10-30 seconds depending on their launch trajectory. Howitzer-launched artillery flares (such as American M119A1 or the Russian D-30) generally lasted longer and also were far brighter than their UGL counterparts.
While no longer as necessary due to the prevalence of night vision equipment for almost every BLUFOR and specific Russian units, they were still important to carry for low-tech factions such as the Takistani Army or NAPA and Chedaki guerrilla/insurgent fighters.
Unlike in Cold War Assault, most rotary and fixed-wing aircraft alike were fitted with flare launchers to ward off IR-guided missiles. These were usually paired to Infrared Warning Recievers (IWRs) which help to alert the pilot of being locked onto by incoming missiles, though not all aircraft were fitted with the necessary avionics to do so.
Aircraft flares were still quite random with regards to their effectiveness, as they could either work extremely well against IR missiles like the American AIM-9L Sidewinder/Russian 9K38 Igla, or were completely useless even while the aircraft was flying fast and making hard manoeuvres.
ArmA 3 flares also functioned very similarly to their ArmA 2 counterparts, though the flare effect was changed to become more pronounced and clearly identifiable at long distances.
Unlike in ArmA 2 however, UGL flares were changed once again to be like their Cold War Assault counterpart in that they could be loaded by all UGL-equipped rifles like the CSAT Katiba or the AAF's Mk20. 3-round flare rounds were also made available specifically for use on the MX's 3GL grenade launcher.
In general however, UGL flares were once again not as useful or as necessary in ArmA 3, due to the availability of hand-thrown chemlights and how common NVGs are for almost every unit and vehicle on the three main factions.
While there are no static howitzers in ArmA 3, self-propelled howitzer vehicles such as the CSAT 2S9 or NATO M4 had the ability to launch more powerful, longer lasting flares over extreme distances while being able to remain on the move. The Mk6 Mortar could also function in the same way (albeit as a static weapon that required disassembly) and could only launch smaller 82 mm flare mortars instead.
Aircraft flares functioned exactly the same as their ArmA 2 counterparts, though the introduction of the new aircraft sensors added in the Jets DLC made launching flares slightly more useful since they used a pseudo random system in addition to relying on the aircraft's position (though still with a degree of unpredictability to their effectiveness regardless).