The Kremlin warned Monday against “nuclear rhetoric” after President Trump repositioned two nuclear submarines because of what he called “foolish and inflammatory statements” by former Russian president Dmitry Medvedev.

In a social media post, the president described the move as a deterrent prompted by threats by a former Russian leader. It is unclear if any submarines did actually change position.

Can one seismic shock upset the equilibrium of nuclear deterrence? That question was brought into stark relief by the recent 8.8-magnitude earthquake off Russia’s Kamchatka Peninsula, which pounded the Rybachiy submarine base,