As the 1st Brigade Combat Team of the U.S. 82nd Airborne Division departed for the Middle East amid rising tensions with Iran, their divisional commander gave a simple order. All personnel entering the region were told to leave smartphones and personal devices in the United States.

It was a clear sign of growing official nervousness over the potential vulnerability of items that had become an unquestioned fact of life for soldiers and civilians alike, but which Washington fears potential foes could track, exploit and use for targeting. Such concerns are far from new but were regarded less seriously when America's primary enemies were seen as nonstate groups such as Islamic State, the Taliban and al-Qaida. Now Washington is worried about other nations — not just Iran, but Russia and China — which are seen as a much more existential threat.

It also points to a much greater trend. Across the board, the communications revolution — and the vast sea of data it produces — has made surveillance much easier, a trend likely to be magnified by the growth of artificial intelligence.