Throughout Donald Trump's presidential campaign, and now during his first weeks in office, one country keeps re-emerging in the controversies that swirl around him: Russia.
For all the turbulence, Trump and his team have not addressed the larger and more important questions of how they plan to deal with Vladimir Putin's Russia on a host of critical issues: the war in Syria, the turmoil in Ukraine, the future of NATO.
The latest episode was Monday night's resignation of national security adviser Michael Flynn. Even as Trump contemplates Flynn's replacement, Defense Secretary James Mattis flew out of Washington before dawn on Tuesday to reassure European allies anxious over Trump's campaign criticism that NATO is "obsolete."
Many NATO members find such remarks particularly troubling in the aftermath of Russia's 2014 annexation of Ukraine's Crimea region and its ongoing support of separatists in eastern Ukraine.
Yet Trump has often appeared more critical of NATO than of Russian actions seen as destabilizing Europe — something other foreign policy voices have seized upon.
"American policy toward Russia must be made clear and unequivocal: we will honor our commitments to our NATO allies, we will maintain and enhance our deterrent posture in Europe, we will hold Russian violators of human rights accountable for their actions," Arizona Republican Sen. John McCain said in a statement Tuesday.
A softer line on Russia
Under his tag line of "America first," Trump talks tough about many countries, from building a wall on the Mexican border to imposing trade tariffs on China and freezing immigration from mostly Muslim countries.
Yet Trump has consistently opted for a much softer line on Russia, out of step with both Republicans and Democrats who see Putin as challenging American interests on multiple fronts.
The Russians are again staging extensive airstrikes in support of Syria's President Bashar Assad, part of a campaign that has been widely criticized for the many civilian casualties and frequent hits on hospitals.
Critics also say the Russians have often struck at moderate rebels who threaten Assad's army, while largely ignoring the Islamic State, which is concentrated in the thinly populated eastern part of the country.
Trump has refrained from criticizing Russia's role in Syria as well. He has ordered the U.S. military to come up with a new, comprehensive plan for the U.S. to defeat ISIS and suggested that the Americans and the Russians could join forces.
And in Capitol Hill testimony last Thursday, the top American commander in Afghanistan, Gen. John Nicholson, said that Russia was providing assistance to the Taliban insurgents battling the U.S. forces and the Afghan government.
Asked about the Russian motives in Afghanistan, Nicholson said, "I think it's to undermine the United States and NATO."
While the general did not go into details, it was clearly a frustration in a war he called a "stalemate."
Trump has gone out of his way on multiple occasions to avoid criticizing Putin.
When Bill O'Reilly of Fox News recently said, "Putin is a killer," Trump replied: "There are a lot of killers. We have a lot of killers. Well, you think our country is so innocent?"
Trump went on to say of Putin: "I do respect him. Well, I respect a lot of people, but that doesn't mean I'll get along with them."
While Russia looms large in all these foreign policy matters, Moscow has also been central to Trump's political intrigues at home.
Here's the briefest of recaps:
-- Russia was accused of hacking into Democratic Party emails and trying to undermine Hillary Clinton in the election, a charge Trump has been reluctant to accept and which has become the source of quarrels with U.S. intelligence agencies.
-- Paul Manafort, Trump's campaign chairman, denied reports that he was paid by pro-Russian interests for work he did previously in Ukraine. But he resigned from Trump's team in August.
-- Trump's secretary of state, Rex Tillerson, has faced criticism from many Democrats for the close ties with Putin he cultivated as the chief executive of Exxon Mobil.
-- U.S. intelligence officials informed then-President-elect Trump about a dossier, compiled by a former British intelligence officer, that alleges the Russians have compromising material on Trump. At the time, U.S. officials said the claims are unconfirmed, and Trump angrily dismissed them.
So far, Trump and Putin have just had one phone call, on Jan. 28, where both leaders said they would like better relations after years of friction.
But Flynn's flameout has contributed to a sense of turmoil in the White House, a Congress suspicious of the president's intentions, and a fog of uncertainty around how Trump plans to engage with Russia.
Greg Myre is a national security correspondent. Follow him @gregmyre1