Of the myriad responses to American military strikes against the regime of Syrian strongman Bashar al-Assad, one is subject to particular scrutiny by foreign policy watchers: Russia's.
Put simply, Syria matters more to the Kremlin than anyone other than Syrians themselves.
"Russia can't afford anything that diminishes their status in Syria and in the region," said Michael Bell, Canada's former ambassador to Jordan and Israel and an adjunct professor of political science at the University of Windsor.
With U.S. officials raising the prospect of further economic sanctions and musing about Russia's role in chemical-weapon attacks against civilians, the Russian missile frigate Admiral Grigorovich entered the Mediterranean on Saturday for what state-controlled media called "a routine voyage."
As Elliot Tepper, professor emeritus at Carleton University's Norman Paterson School for International Affairs, put it, "the Russians want to be the deciders, and in their mind they're going to be the deciders … we're now faced with the possibility, and I must emphasize possibility, of Russia escalating the conflict."
So why is Syria so important to Russian President Vladimir Putin?
Domestic politics in Russia
All politics is local, and Mr. Putin's popularity at home is a function of a political doctrine from which Mr. Trump later took a page: Make Russia great again.
The Russian economy has been ravaged by falling oil prices. Protest movements appear to once again be gaining steam.
Projecting Russian military power can be a balm to a restive populace, as Mr. Putin doubtless understands from past adventures in Ukraine and elsewhere.
"It's fairly clear an activist role by Putin in the Middle East plays well at home," Mr. Bell said.
It's also no secret Mr. Putin and his intelligence services are seeking opportunities to curb American influence and to undermine the North Atlantic Treaty Organization.
It's understandable that Mr. Putin would see Syria as a good place to test Western resolve, because the last time it happened, the West was found wanting.
Middle East power politics
This is a complicated part of the world, and Syria is perhaps its most complex nation: a patchwork of competing tribal and religious groups that number in the hundreds.
Syria's descent into failed-state status created a power vacuum in large swaths of the country, primarily filled by the so-called Islamic State and its allies.
Another leadership void, created in part by U.S. reluctance to engage in a shooting war in 2013 under president Barack Obama, was quickly exploited by Russia.
It is now a dominant regional power broker. That's not an uncontested position.
"Whether the U.S. acted emotionally doesn't diminish the consequences of what just happened," Mr. Bell said. "It's going to force other countries to overcome the Obama deficit, the unwillingness to intervene."
In the broader sectarian conflict in the Islamic world between Sunnis and Shias, Russia has found common cause with Iran, the most powerful Shia country in the region, since the 1980s. The Syrian civil war pits mostly Sunni rebels against a Shia-aligned regime.
Sunnis far outnumber Shias in the Muslim world, and indeed in Syria, but the House of Assad is part of an "axis of resistance" with Shia leaders from Iraq, Iran and the Iranian-funded Lebanese extremist group Hezbollah. On the other side stand Saudi Arabia, Egypt and their allies.
"What began as an uprising against a dictatorship in the Arab Spring became a civil war, which became a proxy war between Sunni and Shia, which has now drawn in the Great Powers," Mr. Tepper said.
He continued: "This is potentially momentous … we're witnessing the phenomenal collapse of the post-First World War nation-state system in the Middle East."
Location, location, location
Syria's geography matters.
The naval installation in the port city of Tartus, first established in the Cold War, provides Russia's only access to the Mediterranean, crucial for both commercial and military purposes.
Earlier this year, Mr. al-Assad struck a deal to confer territorial sovereignty of the base to the Kremlin, which has plans to expand capacity to host large warships, including aircraft carriers.
There is also a Russian air-force base near the northwestern city of Latakia; it was built essentially from scratch in 2015 and is home to more than 1,000 personnel.
Syria also provides the Iranian Navy's only direct Mediterranean access.
Importance of natural gas
Pipeline politics are a factor in Syria.
The largest natural gas field in the world lies under the Persian Gulf and is shared by Iran and Qatar, the latter of which has forged close ties with the European Union.
Qatar, Saudi Arabia and Turkey would like to build a link, but it necessarily passes through Syria.
Mr. al-Assad and his Iranian and Russian allies have a competing proposal for a pipeline route.
Given that Syria's economy has all but collapsed amid six years of brutal military repression, the resource business takes on a special lustre for anyone who would wish to rebuild the country.
Two weeks ago, Russia and Iran held high-level talks about deepening their energy ties.
As Middle East expert Milad Jokar pointed out in a recent article, "Europe has significant gas energy needs and a quarter of it comes from Russia."
Needless to say, Gazprom, the Russian resources giant, is closely linked to Mr. Putin.
Russia's political and economic incentives are to support the status quo, which for now means their ally, Mr. al-Assad, who is from the minority Alawite sect and has held onto power thanks partly to Christian and Druze minorities.
"Russia's commitment is less to the Assad family than to that kind of regime," Mr. Bell said. "They can't afford to be unseated, but they also don't want a confrontation with the Americans."
Russia's next move
In Mr. Bell's mind, the key question for Russia now is identifying the other circumstances where the U.S. might be ready to intervene.
The Trump administration's apparent unpredictability complicates the equation. Was this a one-off? Does it represent a change in policy or just in attitude?
In any case, Syria is an intricate puzzle, one that is hard to view through the prism of Western sensibilities.
"It's a like a dense web that you can't read," Mr. Bell said. "And that web keeps growing."