In the 21st century aerial, and space based, surveillance and reconnaissance equipment has become much more effective, which has made it more difficult and expensive to use cheap decoys of weapons and vehicles to deceive aerial surveillance. There are still firms that develop and manufacture effective fake vehicles, artillery and anti-aircraft systems but the cost of these fakes has gone up 5-10 ten times faster than the cost of the original items. This is because the aircraft and space satellite sensors have become more powerful and able to detect a lot more details. It was no longer enough to just have a lot of convincing, from the air, inflatable armored vehicles and artillery.
Current sensors, first developed to survey farmland or search for new resources from the air or space, use radars and sensors that can identify what is down there and what it is made of. Worse for the military these multispectral sensors can identify what is below foliage, like forests or jungles as well as camouflage nets. The higher resolution sensors can also detect the tracks armored vehicles or heavy trucks leave on the ground or even the wear heavy tanks leave on paved roads. It gets worse, because new fire control and target selection systems use computers and software to find patterns indicating what enemy forces have been or are planning to do. These systems can also be used to spot deceptions on the ground.
Israel gave a demonstration of how effective these new systems are during the recent 15-day war with Hamas in Gaza. The Hamas surprise rocket attacks were much less effective than during the 51-day war in 2014. Although Hamas fired over three times as many rockets than in 2014, Israeli casualties and losses were much less than in 2014. Hamas losses were higher, especially in terms of tunnels and bunkers located and destroyed, often only after Hamas gunmen or leaders were detected taking shelter in them. Over the last decade software has replaced humans in analyzing aerial digital photos along with data obtained from more abundant and powerful electronic sensors. The use of digital photos made it possible to use software systems to look for threats and even their patterns of operation.
Many nations still maintain stockpiles of inflatable vehicles that could deceive 20th century aerial surveillance but these decoys are now worse than useless because they are more likely to reveal your deception efforts than provide any effective deception. In short, ground deceptions have become less effective and a lot more expensive. There is still some use of these deceptions but they cannot be used as frequently on as large a scale as in the past.
In the early 20th aerial reconnaissance revolutionized the ability to spot, count and even identify enemy forces and bases far from the front line or advancing troops. Before aerial surveillance you were dependent on mounted scouts who operated as close to the enemy as possible to count and identify the opposition and ride back to report what was there. A century ago, horse mounted scouts were supplemented and often replaced by airborne scouts, so aerial combat developed in an effort to keep enemy air observation away from your own rear area.
Senior commander quickly discovered that it was impossible to keep all enemy recon aircraft from getting a look, and often photos, of what was behind the front lines. This made it more difficult to plan surprise offensives, or even protect vulnerable rear-area targets like headquarters, supply storage sites and the hundreds of towed artillery weapons set up in the open to provide support fire for front line troops. Users of aerial recon soon discovered that there were ways to effectively deceive aerial surveillance and the post-Soviet Union forces were the first to discover how much had changed.
While the Russian armed forces were not able to buy many real tanks or warplanes in the two decades after the Soviet Union collapsed in 1991, they still bought fakes. Russian firms that designed and produced inflatable tanks and aircraft were still in business and they had new designs that were real enough looking that they could deceive human analysts who scrutinize aerial photographs. Actually, Russia had lots of these in storage after 1991, but a decade ago they were again buying more tanks and aircraft that were improved models and realized they had to replenish their stock of fakes as well.
All this goes back to the World War II era, when dummy tanks and trucks were widely used and often made of wood and cloth. These were fragile and difficult to set up. Soon came the rubber, inflatable decoy. These were much lighter, easier to set up and could be easily moved about once deflated and packed. In addition, a special trailer was built that created realistic marks on the ground showing characteristic tank "track" marks. The trailer would be towed to where each rubber tank was to be set up. With that, the enemy photo analysts would be convinced that the rubber tank was real, for there behind it were the characteristic marks on the ground that only heavy trucks or armored vehicles tank leave. The military advantages of this deception were substantial. If the enemy recon aircraft spotted hundreds of tanks, enemy plans would have to be changed to deal with this threat.
The Allies used the rubber tank ploy against the Germans many times and as a result, the Nazis always overestimated the number (already substantial) of forces the Allies had. The Germans could have been a lot more aggressive against the Western Allies were it not for the rubber tanks. The presence of these "additional" tanks forced the Germans to hold back large numbers of their own forces as a reserve to deal with fake Allied forces represented by rubber tanks and other deceptions.
Of course, the rubber tanks never saw combat, aside from being shot up by German aircraft a few times and the German armored units being held in reserve were often pounded by Allied aircraft before the panzers ever got to reach the real Allied forces. Many Allied soldiers in 1944 and 1945 owed their life to rubber tanks, and most were never aware of it. For example, in preparation for the final Allied offensive in Italy in 1945, an entire dummy armored division was assembled in the rear of an American Infantry Division, with a highly regarded (by the Germans) Japanese-American regiment attached, convincing the Germans that the main attack was to come on the west coast, rather than in the center. Like any good deception, the use of the rubber tanks was kept secret as much as possible.
For the rest of the 20th century the rubber tanks were still used. In the late 1980s the U.S. Army developed a decoy version of the M 1 Abrams tank. It cost only $3,300 and weighed 23 kg (about 50 pounds). When disassembled the dummy tank is about the size of a duffel bag, while its portable generator is about the size of a small laser printer. When erected, which could be accomplished by two men in a few minutes, the decoy not only looks like a real M-1 (at least from the front), but also simulates its heat signature, to fool infrared detectors. What's more, it can take several hits and remain standing, giving the illusion that you missed, or that there are more enemy tanks around than you thought. Developers of air or space-based sensors took note and began equipping their aircraft and satellites with systems that identify the improved fakes.
While rubber aircraft were not a big item during World War II, fake tanks were easier to build and inflate to the right shape than they are today. And with the high speed of modern combat, attacking bombers often don't notice the peculiar effect their bombs and missiles have on the aircraft they were hitting on an enemy airfield. During these attacks, the parked aircraft might be fake, but the anti-aircraft fire isn't. While the aircraft lost on the ground were cheap imitations, the attacking aircraft shot down were not. Rubber aircraft, then, can be quite lethal. Sort of like cheap bait.
All this began to change in the 1990s as guided bombs and missiles replaced unguided bombs and the need to deal with enemy air defenses. More effective airborne sensors made it easier to get accurate assessments of damage done by aerial attacks.
There have been fewer opportunities to use the ground-based deceptions, especially the new ones and that meant fewer opportunities to see how effective aerial attack and surveillance has become. The recent Hamas campaign revealed how current ground-based deceptions are in trouble and that has military leaders and their staffs paying attention.