There are countless opportunities for such errors in the chaos now overtaking Ukraine. The Russians might shoot at NATO aircraft after misidentifying them. Or they might incorrectly believe that Russian aircraft have been attacked by NATO forces. They might suffer a misfire or a targeting error of some kind that puts Russian ordnance on NATO territory. Europe’s a crowded continent, and no place for a jumpy trigger finger, but accidents are an unavoidable part of warfare.

Any one of these mishaps could lead the Russians, or the United States, or both, to increase the alert status of their nuclear arsenals. This would mean that nuclear weapons and their crews—in some cases, with missiles that are already capable of being launched in 15 or 20 minutes—would heighten their vigilance and readiness to proceed with their missions. Such alerts are rare, and for good reason: They move us one step closer to nuclear conflict.

Finally, there is the frightening possibility that Putin will increase the alert status of his nuclear forces for his own reasons, leaving the Americans no choice but to raise their alert status. The invasion of Ukraine was preceded by the Russian Grom (meaning “thunder”) drills, a regular exercise held by Russia’s strategic nuclear forces. The timing was no accident; Putin relies on Russia’s nuclear deterrent as one of its last claims to superpower status, and he could activate another such exercise, or call for a heightened alert condition, if he thinks things are going poorly for Russia.