A number of ominous theories have emerged after Russian tanks and equipment bearing mysterious "Z" symbols were observed as fears of all-out war mount.
In recent days, military experts have grown increasingly concerned about a recurring symbol appearing on Russian tanks, weapons, supply vehicles and fuel trucks massing at the border with Ukraine as tensions continue to rise.
Aric Toler, a reporter from Bellingcat, a Netherlands-based investigative journalism group, noted that some Russian vehicles but not others have been marked out with a white square and a "Z" over the top.
Toler said his news organisation had "been monitoring this stuff non-stop for eight years" and has no idea what they [the Zs] are, and hadn't seen it before.
Some have referred to it as the "Zorro squad", while others have speculated that the ominous signs are a way to make sure Russians can tell their own vehicles apart from their enemies.
This was a practice employed by the Allies in World War II to reduce the chance of soldiers firing on "friendly" forces, and was also used by UK and US forces in the First Gulf War.
A military insider based in Kyiv told The Sun the tactic suggested "final preparations are complete".
"It's vital that any attacking force can be distinguished, particularly from the air where Russian forces will have complete control," the source told the publication.
"The Ukrainians have very similar tanks and vehicles and will want to reduce the risk of friendly fire."
Today David Kime, a former soldier, police officer and field intelligence officer, has taken to Twitter to share several new theories.
One, reportedly coming from "mercenaries" from the Wagner Group – a Russian paramilitary organisation whose contractors have reportedly participated in a number of conflicts – suggests the "Z" stands for Zelensky – a reference to Ukrainian president Volodymyr Zelensky, Russia's current top enemy.
Another, more alarming theory is that the "Z" represents "the point of no return", while some believe the markings could indicate vehicles allotted to specific roles, or even the formation of a new fighting unit.
Adding to the mystery is the fact that the letter "Z" doesn't actually exist in Russia's Cyrillic alphabet – but regardless, the markings have seen the latest movements by Russia dubbed "Operation Z", with almost 200,000 troops now positioned within striking distance of Ukraine.
That's despite Russian President Vladimir Putin's repeated denials that Moscow was preparing to invade.
It comes as the Ukrainian Joint Forces Command has claimed Russian-backed separatists launched "heavy armament fire' against their own territory, in a bid to "falsely accuse" Ukraine and escalate the crisis.
"With Ukrainian defenders refraining from any aggressive acts that could possibly trigger a violent response, the occupation forces continue to destroy civilian infrastructure on the temporarily occupied territories and sporadically shell civilian settlements," the Command said, according to CNN.
"By doing so, the occupation forces once again demonstrated their cowardice and complete disregard for the lives and health of the local civilian population."