President Obama is on a three-day visit to Alaska that will include a stop north of the Arctic Circle. The focus of his trip is climate change. Some of my Senate colleagues and I recently returned from the Arctic, and while we saw the challenges of melting polar ice, we also saw a greater and more immediate threat. It is a menace that many assumed was relegated to the past: an aggressive, militarily capable Russian state that is ruled by an anti-American autocrat, hostile to our interests, dismissive of our values, and seeking to challenge the international order that U.S. leaders of both parties have maintained for seven...