JOINT BASE ANDREWS, Md.—President Donald Trump leaves Tuesday morning for a seven-day tour through Europe that will begin with him confronting jittery NATO allies over military spending and end with a summit with President Vladimir Putin that will seek to reset U.S. relations with Moscow.
The trip will showcase two foreign-policy thrusts of the administration: Mr. Trump’s contention that the U.S. has been unfairly treated by its European allies on trade and security, and his interest in improving relations with Russia, despite...