Radio communication is the special ability of the selected units in Steel Division 2. Few units are equipped with radio allowing you to increase the range of exposure of skills. Of course, this does not mean that the rest of the troops do not have a radio - your troops inform you about their status, as well as the movements of enemy troops.
The radio ability is unique to some types of units: commanders, leaders, artillery observers, and individual artillery units. In the case of the commanders, increase the range of the control circuit, so that more units will have access to aura of command (+2 experience points). In turn, the artillery will be able to conduct better-aimed targeted fire. The commander and leaders must remain within their radio range to transmit information. Each unit can be a "relay" if it is in the range of the other units. Thus, a chain is formed that you can unfold over the entire map, and the commander will be able to station securely in the rear of the front.
Radio allows your mortars, artillery, and self-propelled guns to use corrected shot. Thus, the accuracy of your units and fire rate will increase twice, and the aiming time will be reduced. Of course, you can still use a normal, non-fixed shot (if you want to cover a larger area with fire). Just press and hold the CTRL key until the order is issued. Each unit with a green radio icon generates the firing zone field. It can be both observers, and artillery groups. Some units of commanders also have a radio and can support artillery.
Remember, however, that some artillery units do not have a radio and cannot use corrected shot, even if you have artillery observers. The same goes for units that call for artillery support from behind the map.
Not only artillery observers have a radio and can correct artillery fire. Some leaders, scouts, planes or even commanders can help with artillery. In the picture, white lines point to an area where the artillery can shoot more accurately (1).
Using the radio and correcting the shot is quite simple: Summon a unit of observers in the "Artillery" section and set them next to your target, for example, a strategic point in the city. The observer does not have to see the target - it's enough for the target area to be within the radio range. Units that fire at targets in this field can take advantage of the corrected shot. The distance between the observer and your squads doesn't matter (although artillery still can't shoot any further than the maximum range value). It is necessary to put observers together with intelligence units in the shelter and keep them alive as long as possible (preferably behind enemy lines). Precise artillery fire is extremely useful in eliminating enemy artillery, its anti-aircraft, and anti-tank cannons.