Russia’s nuclear submarine called Belgorod has left its White Seabase. NATO (North Atlantic Treaty Organization) has warned that the sub might be on a mission to test the Poseidon drone.

NATO has warned all member states that the nuclear-capable submarine has deployed. The Belgorod has disappeared from its home base in the Arctic Circle and may be on its way to the Kara Sea to test the Poseidon nuke,  a NATO warning note leaked to Italian media over the weekend has suggested. According to a report by The Daily Mail, Poseidon is a drone that is said to be capable of traveling huge distances underwater before detonating with enough force to trigger a 1,600ft nuclear tsunami designed to drown and irradiate coastal cities.

NATO has since sent a warning to all allies that the sub has gone missing, but said it is still thought to be operating in the Arctic. It is unclear exactly when the warning was sent, but it was first reported by the Italian newspaper La Repubblica on Sunday.

The Belgorod submarine has been in operation since July. It was originally suspected that this sub played a role in the destruction of the Nord Stream pipelines. However, its absence would have been immediately noted and it would have had to travel over 3,000 from the Arctic to damage the pipelines in the Baltic Sea.

The Poseidon warhead has never been tested due to international prohibitions on the testing of nuclear weapons. Breaking with those treaties by testing Poseidon, even in the remote waters of the Arctic, would be a hugely provocative move by Russia. It would also solidify its promise that it is not “bluffing” when it comes to taking actions to protect Moscow.

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Russia may not be testing the nuclear warhead either. It could be simply showing force towards NATO and the West.

Additionally, a huge freight train moving specialist military equipment associated with a nuclear-arms-wielding division of Russia’s Defence Ministry has been spotted on the move, prompting fears of an escalation in the war. A series of BPM-97 armored personnel carriers (APCs) and other military vehicles were seen traveling through central Russia in a clip posted on the Telegram messaging app by the pro-Russian channel Rybar on Sunday according to a report by The Daily Mail. 

Military analyst Konrad Musyka claimed the deployment of such units could signal a coming escalation in the conflict or constitute a precursor to large-scale nuclear drills. Neither is good.