KYIV, Ukraine (AP) — On Ukraine's battlefields, the simple act of powering up a cellphone can beckon a rain of deathly skyfall. Artillery radar and remote controls for unmanned aerial vehicles may also invite fiery shrapnel showers.

This is electronic warfare, a critical but largely invisible aspect of Russia's war against Ukraine. Military commanders largely shun discussing it, fearing they'll jeopardize operations by revealing secrets.

Electronic warfare technology targets communications, navigation and guidance systems to locate, blind and deceive the enemy and direct lethal blows. It is us...