Historically, the term “special relationship” has been reserved for the U.S. and Great Britain. But while Brexit voters may have much in common with Red State America, on a leadership level, it is Trump and Abe who have much in common. Like President Trump, Prime Minister Abe campaigned on being an agent of change, unafraid to challenge conventional wisdom and focused on sweeping economic and political reforms to revitalize Japan. Also like Mr. Trump, Mr. Abe rejects the notion that the conventional rules of politics and foreign policy are sacrosanct. Instead, he has challenged decades-long policies and become the boldest Japanese leader since the end of World War II.

Mr. Abe’s reforms are now poised to have an enormous impact on U.S.–Japanese cooperation, particularly regarding defense and trade. In the face of fierce opposition, Mr. Abe has lifted major post-war restrictions on Japan’s self-defense forces. Japan can now actively participate in its own self-defense and provide support to U.S. forces in Asia. Mr. Abe has also established or enhanced bilateral defense ties with India, Australia, Vietnam, and the Philippines to counter China’s military build-up and is providing new support to Japan’s defense-technology sector.

These national-security reforms come at a crucial time. As Mr. Trump and Mr. Abe prepare to meet, the U.S. and Japan face an Asia in turmoil and perhaps the most dangerous global security environment since the end of the Cold War. Asian security challenges alone include a rogue North Korea with a growing nuclear capacity to threaten both Japan and the U.S., and Chinese territorial assertiveness in the East and South China Seas, along with expanded military installations and a navy increasingly capable of projecting power, as well as growing Chinese military capabilities in cyber, space, and electromagnetic-pulse warfare. In addition, the current Philippine government is openly hostile to U.S. alliances in Asia, while Russia has installed anti-ship missiles in the Kurile Islands, whose sovereignty has been continuously disputed between Russia and Japan since the end of World War II.