Columnist

One simple rule for decoding foreign policy is that presidential trips often drive the agenda. So the fact that President Trump is planning to visit Beijing and other Asian capitals in just over a month may tell us more about what's ahead in that region than all the tweets, rumors and palace intrigue.

War with North Korea? It's a scary possibility, for sure. But a president who is preparing for a grand meeting in November with Chinese President Xi Jinping won't want to fly there through a cloud of nuclear fallout. Will Xi deliver on his promise to pressure Pyongyang beforehand? The trip plans make that more likely than some analysts think, given that Xi and Trump want a Mar-a-Lago 2.0 that celebrates joint efforts on regional issues.

And what about Secretary of State Rex Tillerson, the gray man of Trump's foreign policy team and the subject of ceaseless rumors that he will be fired? Well, he was on his way to Beijing Thursday to prepare the way for the Trump visit. It's unlikely that the Sherpa will be thrown off the mountain before the president reaches the summit.

The hardest challenge in following this chaotic White House is separating actual policy from the "House of Cards" backbiting that surrounds the president. Trump seems to operate with what might be called an "iron whim," becoming enraged about perceived slights and oversights, fulminating one moment and threatening retribution — but then turning to something entirely different.

These presidential cycles of favor and disfavor seem to change almost daily: Trump publicly insults Attorney General Jeff Sessions but continues to work with him. He rages at Senate Majority Leader Mitch McConnell (R-Ky.) and flirts with his Democratic rival, Sen. Charles E. Schumer (D-N.Y.), and then a few weeks later discards bipartisanship and panders to his GOP base. Most recently, he was all in for Luther Strange in Alabama's Republican Senate primary until he wasn't.

At the center of this perpetual White House hurricane have been Tillerson and Defense Secretary Jim Mattis, who in the administration's first weeks lashed themselves to each other and to the mast of policy. That alliance seems as steady as ever, even as the rumors fly that the president is about to throw Tillerson overboard in favor of U.S. Ambassador to the United Nations Nikki Haley. That Cabinet shuffle may happen eventually, but it's unlikely now, when Tillerson is stewarding the China trip and diplomatic strategy for North Korea.

The politics of travel helps explain another policy knot. Trump's first overseas destination was Saudi Arabia, and he loved the royal pomp that greeted him. He invested heavily in Crown Prince Mohammed bin Salman as a change agent — a Trumpian disrupter of the status quo in Saudi Arabia (who delivered "bigly" with this week's announcement that women will be able to drive).

When the Saudis and the United Arab Emirates decided to squeeze their troublesome neighbor Qatar, Trump instinctively sided with Riyadh. Tillerson initially peeved Trump by leaning the other way, arguing that this dispute should be mediated. But by this month, Trump seemed to have come around to Tillerson's viewpoint and was talking on the phone to King Salman and in person to Qatar's ruling Sheikh Tamim Bin Hamad al-Thani to say that it was time to resolve the dispute. An effort last week failed, but there will be another.

Trump still leans toward Riyadh, but he knows that Tillerson and Mattis have a united front on this issue, as on most others. The Tillerson-Mattis relationship remains the balance wheel of this administration. Trump may get angry, as after Tillerson's comment that the president spoke for only himself after the Charlottesville unrest. But it's said that Trump watched the video of Tillerson's remarks three times and decided he was "okay with them," though he may still be quietly grumbling.

Tillerson remains mystifyingly reluctant to use the communications tools that are an essential part of U.S. foreign policy. The latest example was the way he ceded control of refugee policy, a traditional State Department issue, to White House aide Stephen Miller, who set a cap of 45,000, the lowest in decades. Apparent (unfortunate) message: Tillerson didn't want another open dispute with the president.

In Trump world, we're learning to watch what the president does more than just read his inflammatory tweets. That lesson applies to his itinerary. Watch where he goes, and some of the policy implications become clear. A president who is about to attack North Korea doesn't schedule a November trip to China.

Read more from David Ignatius's archive, follow him on Twitter or subscribe to his updates on Facebook.