Capping another hectic day in Ukraine, it was reported that Russia is amassing forces on a sea crossing separating Russia from Crimea, which was taken as an indication that Russia is preparing to strengthen its hold on the peninsula. Whether it signals a broader Russian push into other areas of Ukraine remains to be seen.

Also, Ukrainian officials claimed that the Russian military had issued ultimatums calling on Ukrainian troops to evacuate bases in Crimea. However, the Russian defense ministry denied the allegation, describing it as "utter nonsense." Ryu Spaeth

The Defense Department is looking into canceling enlistment contracts for 1,800 foreign-born military recruits, about 1,000 of whom no longer have valid visas, opening them to the risk of deportation, The Washington Post reports, citing an undated Pentagon memo prepared for Defense Secretary James Mattis. The memo cites what it calls heightened security threats from the immigrants in the program, Military Accessions Vital to National Interest (MAVNI), launched in 2009 to fill crucial medical and language staffing gaps by offering foreign-born recruits expedited U.S. citizenship in return for military service.

Since its launch, MANVI has brought in more than 10,400 mostly Army recruits to jobs deemed critical for military operations, though the Pentagon stepped up security screenings for recruits in the program last year. Along with canceling the contracts of the 1,800 foreign-born recruits who have yet to be given orders for basic training, the memo suggests canning 2,400 part-time troops in the MANVI program who have yet to attend basic training, and submit another 4,100 — most of them naturalized U.S. citizens — to "enhanced screening," if the Pentagon can navigate the "significant legal constraints" of monitoring U.S. citizens without cause, the memo says.

The 1,000 recruits at risk for deportation have seen their visas expire while waiting for the Pentagon to send them to basic training, and canceling their enrollment would remove their protected status, not just their pathway to citizenship. Also, "the recruits are on government rolls detailing their addresses, phone numbers, and legal statuses, making them prime targets for removal," The Washington Post notes. "It remains unclear if military officials would hand over that information to the U.S. Immigration and Customs Enforcement."

"It's terrible," retired Army officer Margaret Stock, who helped set up the MANVI program, tells The Washington Post. "You trusted the Army, who delayed the process, and now they're going to cancel your contract and have you deported." Pentagon spokesman Johnny Michael told the Post on Monday that the Defense Department is reviewing the MANVI program requires, but declined to elaborate or confirm the authenticity of the memo. You can read more at The Washington Post. Peter Weber

On Monday's Late Show, Stephen Colbert reiterated that he was extremely happy to be back in America after his visit to Russia last week. "The whole trip was supposed to be top secret," he explained. "I'm serious. I wanted to get over there and get back before anybody knew. And some traitor leaked that I was over there. Luckily, after an exhaustive search, we have found the leaker — it was me." He showed the tweet he sent to President Trump showing himself in Russia, apologized to himself, then gave some context: "That's me in front of St. Petersburg's Winter Palace — or as they call it, Czar-a-Lago."

While in St. Petersburg, he was the guest on the late-night talk show Evening Urgant — "It's hosted by the very talented Ivan Urgant," he said. "Ivan, I presume, is Russian for 'Jimmy'" — "and while talking to Ivan, I accidentally made some news on purpose," Colbert said. He showed a bit of his interview, and it included some jokes about Russian election meddling that demonstrated some intestinal fortitude, or perhaps comedic foolhardiness. "Now, to be clear, all I said in that little clip there was that I was considering a run" for president in 2020, Colbert explained. "If I decide to run, obviously I'm not going to ask the Russians to help my campaign, okay? I'd have my son-in-law ask them." He ended with some descriptions of his trip that made his late-night jokes in St. Petersburg seem all the pluckier. Watch below. Peter Weber

Stephen Colbert was in Russia last week, he revealed on Monday's Late Show.

His audience may not have been aware of his travels, but "you know who did know I was in Russia?" Colbert asked. "Russian intelligence — hard-core fans, evidently, followed me everywhere." He explained that he and his crew returned from Moscow Sunday night, that he was still on Russian time, and that he would show some of the several segments he shot there in coming weeks.

"But while Russia was fascinating, it is sincerely wonderful to be back in America," Colbert said. "Let's see what everybody's talking about here. Oh that's right, Russia." He walked through the big Washington Post report that former President Barack Obama knew about Russia's specific plot to tip the election to Trump back in August, but eventually did little to stop it. "President Trump is a well-known Russia-hacked-the-election denier," Colbert said, showing video evidence. So he appeared surprised that Trump went all-in on the idea that Obama did nothing to prevent Russia hacking the election in his favor.

Colbert adopted his Trump-tweet voice and paraphrased: "That's right, there was no Russian hacking, period. #FakeNews. Wait, it was Obama's fault? Russia stole our election and Obama let it happen! Thanks, Obama. No, seriously, thanks, Obama. I'm president now. Thanks!" He read the rest of Trump's tweetstorm, stopping to marvel at Trump's new self-adopted nickname, and his chutzpah. "Hold on, nobody is accusing Obama of 'colluding or obstructing,'" Colbert noted. "That's your deal." Trump also demanded an apology over the Russian hacking, and Colbert agreed: "Look, I'm a big enough man to apologize. And I think I speak for the majority of Americans when I say, 'I'm sorry you're president.'"

Colbert ended his monlogue by noting that White House Press Secretary Sean Spicer is no longer letting his press briefings be recorded. "Evidently, while I was in Russia, we turned into Russia," he said. Watch below. Peter Weber

Late Monday, Brazil's chief prosecutor, Rodrigo Janot, filed charges accusing embattled President Michel Temer of corruption for allegedly taking a $152,000 bribe, with the promise of $11 million more, from meatpacking magnate Joesley Batista. The charges will likely be weighed by the Chamber of Deputies, the lower house of Congress, where a two-thirds majority would be needed to suspend Temer for up to 180 days while he was put on trial. Temer, who replaced President Dilma Rousseff after she was impeached, is expected to get enough support in the lower house to avoid suspension, though Janot is believed to be preparing further charges, to be filed one at a time, requiring votes on each charge. Brazil has no vice president right now, and if Temer is suspended, House Speaker Rodrigo Maia would take over.

Temer is unpopular — a poll last week found his approval number at a historically low 7 percent, with 76 percent saying he should resign — and members of Congress face elections next year. Temer denies the bribery and other charges — including a taped conversation with Batista that reportedly captures him approving payments for the now-jailed former speaker of the lower house — and often notes that Batista got a generous plea bargain to cooperate with prosecutors. This is the first time a sitting Brazilian president has been charged with a crime. Peter Weber

On Monday, the Pew Research Center released a survey on how 37 countries view the United States under President Trump, and overall, the numbers are pretty eye-opening. In the six months since former President Barack Obama left office and Trump was sworn in, favorable views of the U.S. have dropped from 64 percent at the end of Obama's tenure to 49 percent, while unfavorable views rose from 26 percent to 39 percent. It took former President George W. Bush eight years to get numbers that bad, especially in Western Europe, Pew said, but under Trump, the change has been almost immediate.

But the drop in American esteem wasn't universal. In two of the 37 countries, people have more confidence in Trump to do the right thing than they did Obama, Pew found, and the shift is way more dramatic in Russia than Israel.

The other bright spot for Trump is that a 55 percent majority of people in the 37 countries view him as a "strong leader" — though that's below the number who view him as "arrogant" (75 percent), "intolerant" (65 percent), and "dangerous" (62 percent), and above the percentage who see him as "charismatic" (39 percent), "well-qualified to be president" (26 percent), and "caring about ordinary people" (23 percent). Broad majorities disagree with almost all of his main policies.

Foreign views of America matter because they determine how foreign leaders engage with U.S. interests, former diplomat Frank Wisner tells The Washington Post, and Trump's dismissal of traditional U.S. principles has already left a mark. "America's image has taken hits in recent years, from the decision to invade Iraq to the events of 2007 and 2008, when the American financial model took a huge hit," he said. "But the most consequential is the ascent of Mr. Trump to the Oval Office."

Pew conducted its surveys from February to May, and the margin of sampling error varies between countries from ±3.2 percentage points to ±5.7 points. You can read more about the world's views of Trump's America at Pew. Peter Weber

The Senate Republicans' health-care plan is "almost comically villainous," Seth Meyers said Monday night, with its tax cuts for the wealthy paid for by gutting Medicaid.

"The only way this bill could be more cartoonishly evil is if it mandated tying damsels in distress to railroad tracks," he said on Late Night. On Monday, the Congressional Budget Office release its report projecting that the GOP plan would leave 22 million more people uninsured over the next 10 years, and that's "savage," Meyers said, and precisely why Senate Majority Leader Mitch McConnell (R-Ky.) kept the bill under wraps until last Thursday, pushing for a vote sometime this week. "This bill is like a Slipknot tramp stamp," Meyers said. "You definitely want to hide it, and the people who've seen it are terrible people." Watch the video below for more on the CBO score, and how former President Barack Obama sneakily trolled President Trump. Catherine Garcia

The White House appeared to draw a new red line on Syria Monday night, with Press Secretary Sean Spicer warning that Syrian President Bashar al-Assad had been caught making "potential preparations for another chemical weapons attack" that "would likely result in the mass murder of civilians, including innocent children," and if he "conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price." The rest of the government, including the military, appears to have been caught off guard by the announcement.

Five U.S. defense officials "said they did not know where the potential chemical attack would come from, and were unaware the White House was planning to release its statement," BuzzFeed News reports. "Several State Department officials typically involved in coordinating such announcements said they were caught completely off guard by the warning, which didn't appear to be discussed in advance with other national security agencies," the Los Angeles Times reports. "Typically, the State Department, the Pentagon, and U.S. intelligence agencies would all be consulted before the White House issued a declaration sure to ricochet across foreign capitals."

Various agencies and departments referred reporters to the White House for comment. It's "unclear how closely held the intelligence regarding a potential chemical attack was," The New York Times notes, after similarly reporting that "several military officials were caught off guard by the statement" from Spicer. "While the White House's motivation in releasing the highly unusual statement is uncertain, it is possible that Mr. Trump or his advisers decided a public warning to Mr. Assad might deter another chemical strike," the Times suggests, adding that the president has "absolute power to declassify anything he chooses to release," including intelligence on chemical weapons.

At least one Trump administration official appeared unfazed by the statement:

After U.S. intelligence pointed the finger at Assad for an April 4 chemical weapon attack on Syrian civilians, Trump ordered 59 missiles fired at an Assad air base; Russian blamed the anti-Assad opposition, claiming Syrian warplanes had hit rebel stockpiles. Last week, the U.S. shot down a Syrian government warplane after it targeted U.S. allies fighting the Islamic State. Peter Weber