Russian forces have been regularly jamming signals from the U.S. Global Positioning System as part of its war on Ukraine. These signals underly many aspects of modern warfare from navigating surveillance drones and targeting missiles to enabling mobile radios.

The importance of GPS as a military tool was underscored by Kremlin media in November as troops were massing along the Ukraine border. After Russia demonstrated it could destroy a satellite in space, a television commentator known to be an unofficial mouthpiece of President Vladimir Putin said the nation could “blind NATO” by shooting down all GPS satellites.

Experts within the GPS/positioning, navigation, and timing communities have proposed a number of possible reasons for this. Here are the most prevalent, all of which are based entirely on publicly available information:

Russia’s electronic warfare capability isn’t as good as had been thought. Russian forces have a fearsome reputation when it comes to electronic warfare. And they go out of their way to reinforce this. At one point the state-owned news agency Sputnik proclaimed Russian EW capabilities “render aircraft carriers useless.”

Since Russian forces’ have been surprisingly less capable than expected in other aspects of the Ukraine conflict, some think this may be true with their ability to interfere with GPS.

Most observers discount this suggestion, though.

They point out that Russian forces regularly jam GPS signals in northern Norway from locations far across the border. And that in some cases this jamming has been so precise, signals in a nearby frequency band from Russia’s GLONASS satnav system have been unaffected.

A 2016 Moscow Times headline read “The Kremlin eats GPS for Breakfast.” The general consensus in the community is that there has been a lot of evidence to support that claim.

The question is then, why is the Kremlin only nibbling at GPS in Ukraine?

Russian forces use/need GPS. Proponents of this idea point to downed Russian fighter jets found to have GPS receivers taped to their dashboards.

Signals from Russia’s GLONASS satnav system and terrestrial Chayka electronic navigation system are both available for use in Ukraine. Yet it seems likely there not enough compatible receivers for these systems to equip all Russian forces. As the world’s first global navigation satellite system, GPS receivers have become both plentiful and inexpensive. Cheap GPS receivers and some duct tape seems like an interim solution for some poorly equipped Russians.

Also, GPS signals support a wide variety of infrastructure. Telecommunications, internet, electrical grids, machine control systems, all rely on GPS for timing. Russian forces may wish to protect Ukraine’s infrastructure for their own benefit and use. Prolonged and widespread attacks on GPS signals could cause serious infrastructure problems with long term strategic downsides greater than could be offset by any temporary tactical gains.

High power, persistent GPS jammers are easily targeted. Any strong and consistent radio frequency transmission can be easily located and attacked. Many militaries have missiles especially designed to home in on and destroy jamming transmitters. Even without such weapons, direction finding can pinpoint a transmitter enabling an artillery attack, air, or ground assault. Russian commanders may be limiting transmission power and time on air to avoid attracting hostile fire.

Ukraine less impacted. While Ukraine is getting and using more and more western weapons, many of which use GPS, it also has huge stockpiles of Soviet-era weapons. These don’t rely on GPS and are likely unaffected by most, if not all, forms of electronic warfare. Also, Ukrainian regular and irregular forces are likely less reliant upon sophisticated command, control, and communications systems used by larger militaries. Thus, GPS jamming that could hamper normal operations for the U.S. and NATO, may have less impact in Ukraine.

Saving the best to use against U.S. and NATO. Despite the location of the conflict, Ukraine is not the enemy Vladimir Putin is really worried about. His concerns focus on the U.S. and NATO. Deploying Russia’s most sophisticated and powerful electronic weapons in Ukraine would enable adversaries to study technologies and tactics. This would lead to the development of countermeasures and make the weapons less effective in future conflicts.

Better for Russia to keep its best tools and tricks for interfering with GPS in reserve for use later against larger forces and more important targets.

Dana A. Goward is President of the Resilient Navigation and Timing Foundation and serves on the U.S. President’s Space-based Positioning, Navigation and Timing Advisory Board.