The U.S. Marine Corps has solved the problem of the many illumination devices troops attach to their rifles, by combining four of them. The PEQ-16 includes flashlight, IR (or infrared) floodlight, IR designator and visible laser (or red dot) designator in one device. All this began when troops found flashlights and visible lasers were very useful assault rifle accessories.
These flashlights were useful because, when going inside buildings or caves, night vision devices don't work very well. That's because these gadgets just intensify available light. If there is no available light, there's nothing to intensify. So small flashlights are attached to the end of rifles when going into these pitch-black places. These are not your ordinary flashlights, but "white light" models. The white light is more likely to temporarily blind anyone who gets a good look at it, and spoil their aim if they start shooting at the source of the light.
The U.S. Army combined some of these in the MFAL (Multi-Functional Aiming Lights). This looks like a small flashlight, and attaches to the rifle. But this device can put out visible, or invisible (infrared, or IR) light. When using IR, you go into a cave providing light only you can see, with your night vision equipment. If you are real quiet (or sort of quiet), you have a big advantage over the bad guys trying to hide in the dark. This rig also allows you to see any booby traps the enemy may have laid for you. MFAL also emits a laser pointer (like the older "red dot"), but one that cannot be seen by the enemy (unless they also have night vision gear, which they usually don't.) The MFAL was developed with the help of feedback from combat troops in Iraq and Afghanistan. The marines developed a similar device, the PEQ-15, which had IR and laser. The PEQ-16 is the PEQ-15 with a white light added.
The army Integrated Laser White Light Pointer (ILWLP) provides an infrared aiming light out to 600 meters, and an infrared illuminator that will be good for 300-600 meters depending on how much moonlight is available. The infrared illuminator will also be able to light up an interior space of about 400 square feet. For the infrared illuminator, you need infrared lenses on your goggles to see what the infrared light illuminates. A red dot laser is also built into the unit and has a range of 10-25 meters, depending on the lighting conditions. There is also a white light (flashlight) capability, that can allows facial recognition out to 25 meters. Naturally, the ILWLP costs more than ten times as much as the Surefire White Light.
Thus soldiers and marines have found out how to use several different forms of light to make their weapons much more effective. Average use allows these devices to last about two weeks on one set of batteries.