Depending on the war, you might not have cell phone (basestation) signals everywhere during actual fighting, relying on that seems a bit limiting.

Sure because at end of day, radar is all about detecting bouncing radio waves.

However, it's accuracy of detection that changes the battlefield and my guess is detecting disturbed cellular signals gives very low detection chance/range.

Also, if enemy thought it was problematic, hit cellular tower with missile is extremely easy.

Cells are highly directional, and should ideally not be installed facing the sky. Add stealth coatings to the mix, and your return signal may not be enough to detect. Radars use high power emitters.

https://www.rcrwireless.com/wp-content/uploads/2023/08/Pictu...