The commander of a British Army battalion tasked with experimenting with new technologies said that his unit has tested out dozens of ground robots. He concluded that they can be useful, but only for certain missions. And they come with a long list of challenges.

As Western militaries rush to absorb lessons from the war in Ukraine and integrate more uncrewed systems into their respective forces, soldiers are finding that some systems might look good on paper but aren’t effective in all combat scenarios.

Ground robots, in particular, can face weight, navigation, cost, and power constraints that raise questions about when and how they should be…