Amazon’s billionaire founder, Jeff Bezos, played host to Defense Secretary James Mattis today during the Pentagon chief’s swing through high-tech hot spots (and military facilities) on the West Coast.

“A pleasure to host #SecDef James Mattis at Amazon HQ in Seattle today,” Bezos wrote in a tweet.

The subject of the Pentagon chief’s chat with the world’s third-richest person wasn’t disclosed, but one of the reasons for this week’s Western trip was to meet with tech leaders. In addition to Amazon, Mattis is due to visit Google’s main campus as well as Defense Innovation Unit-Experimental, or DIUx, both in Silicon Valley.

During his first-ever visit to DIUx’s West Coast offices, Mattis will meet with tech titans to discuss how the Defense Department can leverage commercial technologies and “further expand initiatives designed to accelerate fielding capabilities to the warfighter,” the Pentagon said in an advisory.

Bezos is a member of the Pentagon’s Defense Innovation Advisory Board. Amazon Web Services provides cloud computing services for a growing number of U.S. military customers, and Bezos has said the prospect of contributing to national security through his Blue Origin space venture is “incredibly motivating.”

Mattis also visited Naval Base Kitsap in Bangor, Wash., home port for a fleet of Trident nuclear submarines.

#SecDef Mattis met with leaders of Commander @SUBGRU9 & spoke with the crew of USS Kentucky @NavalBaseKitsap in Bangor, Washington today. pic.twitter.com/pKHnFRBAif — U.S. Dept of Defense (@DeptofDefense) August 10, 2017

The Defense Department said Mattis received a briefing from Submarine Group 9 leaders at the Kitsap base, and toured the Ohio-class ballistic-missile submarine USS Kentucky.

Such submarines could play a role in the U.S. response to any untoward action taken by North Korea amid an escalating series of military threats. On Wednesday, Mattis issued a statement calling on North Korea to stop considering “actions that would lead to the end of its regime and the destruction of its people.” He said Pyongyang “would lose any arms race or conflict it initiates.”

Mattis, a 66-year-old former Marine general, is no stranger to Washington state: He was born in Pullman, went to high school in Richland (where his father reportedly contributed to the Manhattan Project) and got his bachelor’s degree in history from Central Washington University in Ellensburg.