Who is doing the provocation in the Korean Peninsula?

"The United States pointedly showed off its military prowess over the Pacific and the Korean Peninsula on Sunday in response to North Korea’s launch Friday of a missile capable of reaching the U.S. mainland, a test Pyongyang said was a “stern warning” for Washington to back off from threats and more sanctions. In a sign that tensions are spiraling upward rapidly, the United States flew two supersonic B-1 bombers over the Korean Peninsula as part of a joint exercise with Japan and South Korea. And U.S. forces conducted a successful missile defense test over the Pacific Ocean, sending aloft from Alaska a medium-range ballistic missile that it detected, tracked and intercepted using the Terminal High Altitude Area Defense System."