Azov Sea conflict is chess game with weapons, ships, and people
Russia's aggression over disputed maritime territory with Ukraine is putting Western democracies in a bind
When Russian president Vladimir Putin opened a new bridge linking Crimea to Russia across the Azov Sea in May, Russia said it was to integrate the disputed peninsula - seized by Moscow from Ukraine in 2014 - into Russian infrastructure.
By limiting ships transiting the Kerch Strait beneath the giant central span of the bridge, however, it also gave the Kremlin the ability to control maritime access to an area of water roughly the size of Switzerland.
On Sunday, Moscow used a cargo ship to block entry to the Azov Sea. As warplanes and combat helicopters flew overhead, Russian border patrol boats seized three Ukrainian naval ships after opening fire on them and wounding several sailors.
On Monday, Russia's FSB security service said that the confrontation came after the Ukrainian vessels illegally entered Russian waters; Ukraine denied its ships had done anything wrong.
Russia has now reopened the strait, but the clash was another demonstration of Moscow's appetite to use unorthodox, partially non-military and sometimes non-lethal techniques to redraw the geopolitical map.
It's a strategy Mr Putin's foes - particularly Ukraine - are struggling to counter. Ukraine and its Western allies must now decide how to respond.
Not to do so would strike Russia as weakness and invite yet more aggression. But no side wants a conflict they cannot control - this is much more like a game of chess, albeit with live ammunition, ships, aircraft and human beings in the balance.
The most recent clash points to a growing trend in international relations, where military force, economic power and major building and infrastructure programmes are used alongside cyber weapons, propaganda and more.
Such confrontations can be bloodless - as in the South China Sea - or brutally violent, as in Ukraine's Donbass or the savage Middle Eastern proxy wars of Syria and Yemen.
The Azov Sea crisis will feed into this week's G20 summit in Argentina, which both Mr Putin and US President Donald Trump are scheduled to attend.
As in the South China Sea, where Beijing has used giant engineering works to reclaim islands and build military bases in disputed waters, the Azov Sea conflict has been long building in plain sight.
Work on the bridge began in 2015, the year after Ukraine lost control of Crimea to Moscow.
Putin eventually acknowledged that Russian troops had taken part in the annexation, but continues to deny Moscow's military involvement elsewhere in Ukraine despite widespread evidence to the contrary.
Moscow appears similarly disingenuous over the Azov Sea.
Last week, a senior Russian diplomat accused Western states of deliberately stoking tensions to justify new sanctions.
Like the annexation of Crimea, this maritime version of a land grab is illegal under international law - the Azov Sea had been judged under joint Russian-Ukrainian jurisdiction.
But the reality is that it is now under Russian domination.
Perhaps the most significant response to Sunday's confrontation was Mr Trump's tweet criticising Europe for not paying its "fair share for Military Protection".
European leaders were already defining themselves in opposition to Mr Trump; now they will be angrier.
The US president's face-to-face with Chinese President Xi Jinping had been considered the main event; now any meeting with Mr Putin will be even more closely watched. - REUTERS
The writer is Reuters global affairs columnist