Three months ago, as Ukrainian troops were struggling to advance against Russian forces in the south, the military’s headquarters in Kyiv quietly deployed a valuable new weapon to the battlefield.

It was not a rocket launcher, cannon or other kind of heavy artillery from Western allies. Instead, it was a real-time information system known as Delta — an online network that military troops, civilian officials and even vetted bystanders could use to track and share desperately needed details about Russian forces.

The software, developed in coordination with NATO, had barely been tested in battle.