WASHINGTON — Defense Secretary Pete Hegseth has paused offensive cyberoperations against Russia by U.S. Cyber Command, rolling back some efforts to contend with a key adversary even as national security experts call for the U.S. to expand those capabilities. A U.S. official, speaking on condition of anonymity to discuss sensitive operations, on Monday confirmed the pause. Hegseth’s decision does not affect cyberoperations conducted by other agencies, including the CIA and the Cybersecurity and