As weapons become more deadlier and more able to strike pinpoint targets, smaller targets will be selected for attack. If a radio operator sees a squad of enemy troops a kilometer or more out then he is very likely to call in mortars, artillery or something even bigger. The enemy will do it to the good guys just as quickly.
Ground radar units can detect infantry up to several kilometers away, even if they are not visible. If the detected infantry cannot be confirmed as friendly then they are likely to come under fire from supporting fires. This is a two way street and soon the US military won’t be the only force with ground radar.
Additionally orbital satellites can count eggs on a table. If a satellite can see ground targets (tanks dug in and waiting) it can relay that information to someone who can take advantage of that. Artillery rounds do have shells that can target and destroy tanks. Attack fighters can also be used and so on.
Regular airplanes can have cameras mounted on them so pictures can be taken of enemy positions and equipment. Real time pictures can also be taken and relayed to a commander so he knows the best way to deploy his troops and assets.
Knowing something is there means the target is facing destruction. Cruise missiles and other weapons can be targeted against specific grid coordinates. As technology increases so will the accuracy.
In addition to ground radar, there is a wide array of thermal imagers, motion detectors, metal detectors, sound detectors and so on that can detect a target as elusive as infantry, not to mention tanks and other vehicles. These sensors are currently available to US military units. Some have been available since Vietnam.
An infantryman can come under fire from distant enemy support weapons before he even knows he has been seen. Infantry units can still be elusive and conduct surprise attacks, as can tanks and APC’s. As technology advances these few advantages will be lost unless additional technology becomes available to defeat these sensors. Thermal imagers can be defeated by a metal fence, which looks like a solid wall. Standard issue camouflage uniforms help conceal a fighter’s infrared signature.
Everything known to man that is made by man can be killed or destroyed. In the future battlefield this is not likely to change and as sensing devices become more common and accurate, it will be more and more important to avoid detection by enemy forces.
A few items of note is that humans are the only known creature that has ammonia in its breath. This means sensors could be used to detect and track you by your breathing.
Simple visual camaflouge will not be enough on the future battlefields. Imagine trying to hide from a satellite that can see your foot prints or your shadow. Radar that could detect you for kilometers, metal detectors that can detect the weapons in your hand or the metal in your belt buckle. Sound detectors that are so acute they can hear your heartbeat. Electrical detectors that can detect your wrist watch, and if they can detect you they can bomb you.
It is not a pretty picture.
Currently they are working on a hand held device that can detect a person’s heartbeat behind a wall. Certain satellites can detect underground bunkers using a variation of radar.
What is to stop a starship from taking up a place in orbit and using its weapons to hit ground targets it has detected?
As sensors become more accurate counter-measures will become more wide spread and critical.
For instance the Stealth Fighter is invisible to radar. Perhaps one day they will find a way to make infantry invisible to ground radar. Ground radar could also be defeated by operating in rough terrain, in gully’s and gulches. No sensor is perfect and they can usually be defeated in one way or another. Some times with low tech methods that are embarrassing to the sensor operator. Sound sensors could likely be defeated by ‘screamers’ that are inserted into the area of operations and drown out the sound of moving units, a simple solution to a complicated device.
Here is a list of sensors that might affect the future battlefield, some are realistic some are fantastic;
Cellular (Vs Solid)
Light (spectrum analyzer)
This list is by no means complete but it will give you an idea of how complex it could get.