A military base that loses grid power still needs to pump water, fuel aircraft, and keep its command center online. How long could it do that if outside help stopped arriving? That question is behind the 90-day figure circulating on social media. Some posts claim the Pentagon expects a three-month blackout across the United States. The Pentagon’s announcement gives no such warning.

Defense Secretary Pete Hegseth introduced FORTRESS America on September 30, 2026. One goal is for major U.S. military bases to generate their own electricity so they can keep operating if a cyberattack or sabotage disrupts the civilian grid. The plan also calls for more reliable supplies of military equipment, reserves that forces can draw on in a crisis, stronger defenses for bases and computer networks, and protection for the satellites and radio signals troops rely on.

The 90-day figure surfaced in October, when Fox News reported on planning documents it had reviewed. According to that reporting, the goal is for major military installations in the continental United States to sustain essential work for at least 90 days without outside support. That would require dependable access to water, fuel, electricity, and communications throughout the disruption.

The distinction depends on what the number measures. Ninety days describes how long planners want a base to function on its own. It tells households nothing about when their lights might go out or how long an outage might last.