The Kerch Strait is a crucial stretch of water and one of routine high tension.
It is the entry point for Ukraine into the Azov Sea and the major port of Mariupol but it has been controlled by Russia since the illegal annexation of Crimea in 2014.
A bilateral treaty gives both nations the right to use the strait freely but each side routinely complains about shipping delays and harassment.
The video showing a Russian ship ramming a Ukrainian naval boat, and the aggressive onboard audio that goes with it, is damning.
And, as we've become used to with Moscow, this incident is already rife with claim and counter-claim.
Kiev says it gave Russia advance warning that its three boats would be passing through the straits en route to Mariupol from Odessa. Russia denies receiving this notification.
The video certainly paints the Russian ship as the aggressor but Moscow claims Ukraine deliberately goaded Russia into a response, knowing the world would automatically assume Russia to be the bad guys.
Russia even seemed to contradict itself, first saying the three Ukrainian ships had sailed back to port and then amending that a few hours later to confirm they'd been impounded.
For now the military tension seems to have subsided slightly and it has moved to a diplomatic footing.
The Ukrainian President Petro Poroshenko held a meeting of his war cabinet - it broke up shortly before 2am on Monday morning.
He will ask the parliament in Kiev to enact martial law. That could mean control of TV stations, compulsory military service, a ban on demonstrations and even a suspension of elections for the sake of national security.
Bear in mind at this point, just for context, that presidential elections will be held in four months' time and Mr Poroshenko currently trails in the polls. Martial law is rarely good for democracy.
Russia, for its part, has called an emergency session of the UN Security Council in New York on Tuesday.
This will give Moscow the platform to grandstand and play victim. Of course, any vote against them can be vetoed because Russia is a permanent member.
Regardless of who started it, and why, we might be left with a situation that is beneficial to the political interest of both sides - it serves to be alive to the politics at play here.
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