From bellingcat.com
For US soldiers tasked with the custody of nuclear weapons in Europe, the stakes are high. Security protocols are lengthy, detailed and need to be known by heart. To simplify this process, some service members have been using publicly visible flashcard learning apps — inadvertently revealing a multitude of sensitive security protocols about US nuclear weapons and the bases at which they are stored.
While the presence of US nuclear weapons in Europe has long been detailed by various leaked documents, photos and statements by retired officials, their specific locations are officially still a secret with governments neither confirming nor denying their presence.