(CNN) --
Last fall, as Ukraine recaptured vast tracts of territory in a series of counterattacks, it pummeled Russian forces with American-made artillery and missiles.
To guide part of that artillery, Ukraine developed a homemade targeting system on the battlefield.
A Ukrainian-made piece of software has turned readily available tablets and smartphones into sophisticated targeting tools now widely used in the Ukrainian military.
The result is a mobile app that transforms satellite and other intelligence images into a real-time targeting algorithm that helps units close to the front line fire directly at specific targets.
And, because it's an app, not a piece of hardware, it's easy to update quickly, and it's available to a wide range of people.
US officials familiar with the tool say it has been highly effective in directing Ukrainian artillery fire at Russian targets.
Poland announces shipment of Leopard 2 tanks to Ukraine.
What does it mean for war?
The targeting app is among dozens of examples of battlefield innovations Ukraine has come up with during nearly a year of war, often finding cheap solutions to expensive problems.
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Small plastic drones, whizzing silently overhead, drop grenades and other munitions on Russian troops.
3D printers now make spare parts for soldiers to repair heavy equipment in the field.
Technicians have turned ordinary pickup trucks into mobile missile launchers.
Engineers have figured out how to put sophisticated US missiles on older Soviet fighter planes like the MiG-29, helping to keep the Ukrainian air force flying after nine months of war.
Ukraine has even developed its own anti-ship weapon, the Neptune, based on Soviet missile designs that can target the Russian fleet from nearly 200 miles (320 kilometers) away.
This kind of Ukrainian ingenuity has impressed US officials, who have praised Kyiv's ability to offer "MacGyver" solutions to their battlefield needs that fill important tactical gaps left by larger and more sophisticated Western weaponry.
Ukrainian National Guard servicemen operate a homemade anti-aircraft machine gun to destroy drones in Mykolaiv, Ukraine.
(Credit: STR/NurPhoto/Getty Images)
While US and other Western officials don't always have a perfect idea of exactly how Ukraine's custom systems work, largely because they're not on the ground, officials and open source analysts alike say Ukraine has become a veritable battle laboratory for inexpensive yet effective solutions.
“Their innovation is incredibly impressive,” said Seth Jones, director of the international security program at the Center for Strategic and International Studies.
"Battle Trials of the Real World"
Meanwhile, the war in Ukraine has also offered the United States and its allies a rare opportunity to study how their own weapons systems work under heavy use, and what munitions both sides use to win victories in this hotly contested modern war.
US operations officials and other military officials have also tracked the success with which Russia has used cheap and expendable drones that explode on impact, provided by Iran, to decimate Ukraine's power grid.
Ukraine is "absolutely a weapons laboratory in every sense because none of this equipment has ever been used in a war between two industrially developed nations," a source familiar with Western intelligence said.
"This is a real world battle test."
For the US military, the war in Ukraine has been an incredible source of data on the usefulness of its own systems.
Some high-profile systems provided to the Ukrainians — such as the Switchblade 300 drone and a missile designed to target enemy radar systems — have turned out to be less effective on the battlefield than anticipated, according to a US military operations official. with knowledge of the battlefield, as well as a recent study by a British think tank.
But the US-made M142 multiple missile launcher, or HIMARS, has been critical to Ukraine's success, even as officials have learned valuable lessons about the maintenance repair rate those systems have required under such heavy use.
The way Ukraine has used its limited supply of HIMARS missiles to wreak havoc on Russian command and control, attacking command posts, headquarters and supply depots, has been revealing, a defense official said, adding that the leaders military would study this for years.
Ukrainian service members fire a shell from an M777 howitzer on the front line, as Russia's attack on Ukraine continues.
(Credit: Gleb Garanich/Reuters)
Other key information has been about the M777 howitzer, the powerful artillery that has been a fundamental part of Ukraine's battlefield power.
But howitzer barrels lose their rifling if too many shells are fired in a short time, another defense official said, making artillery less accurate and less effective.
The Ukrainians have also made tactical innovations that have impressed Western officials.
During the first weeks of the war, Ukrainian commanders adapted their operations to employ small teams of dismounted infantry during the Russian advance on Kyiv.
Armed with shoulder-mounted Stinger and Javelin missiles, the Ukrainian troops were able to sneak up on the Russian tanks without infantry on their flanks.
The United States has also closely studied the conflict to gain broader lessons about how a war between two modern nations might be waged in the 21st century.
A High Mobility Artillery Missile System (HIMARS) during military exercises at Spilve Airport in Riga, Latvia.
(Credit: Roman Koksarov/AP)
The operations official said that one lesson the United States can learn from this conflict is that towed artillery, such as the M777 howitzer system, may be a thing of the past.
Those systems are harder to move quickly to avoid return fire, and in a world of ubiquitous drones and aerial surveillance, "today it's very hard to hide it," this person explained.
When it comes to lessons learned, "there's a book to be written on this," said Rep. Jim Himes, D-Conn., a member of the House Intelligence Committee.
"A $10,000 one-way attack drone"
US defense contractors have also taken note of the novel opportunity to study — and commercialize — their systems.
BAE Systems announced that Russian success with its kamikaze drones has influenced how it is designing a new armored fighting vehicle for the Army, adding more armor to protect soldiers from attacks from above.
And different parts of the US government and industry have been trying to test novel systems and solutions in a fight for which Ukraine needed all the help it could get.
Ukrainian soldiers stand by with a US-made Stinger MANPAD (portable air defense system) on the front line in Bakhmut, Ukraine.
(Credit: Pierre Crom/Getty Images)
In the early days of the conflict, the National Geospatial-Intelligence Agency sent five high-resolution, lightweight surveillance drones to the US Special Operations Command in Europe, in case they might be useful in Ukraine.
The drones, made by a company called Hexagon, were not part of the Defense Department's so-called registration program, suggesting the experimental nature of the conflict.
Navy Vice Admiral Robert Sharp, head of the National Geospatial-Intelligence Agency at the time, even bragged publicly that the US had trained a "military partner" in Europe on the system.
"What this allows you to do is go out below the cloud layer and collect your own [geointelligence] data," Sharp told CNN on the sidelines of a satellite conference in Denver last spring.
"Ghost", 24, a soldier from the Ukrainian Army's 58th Independent Motorized Infantry Brigade, catches a drone while testing it so he can use it up close.
(Credit: Leah Millis/Reuters)
Despite intense efforts by a small group of US officials and outside industry, it is unknown if these drones ever made it into battle.
Meanwhile, several military and intelligence officials told CNN they hope the creation of what the US military calls "attributable" drones (cheap single-use weapons) has become a priority for contractors. defense.
CNN's Tim Lister and Alex Marquardt contributed to this report.