On Wednesday, a B-1B Lancer strategic bomber flew from Guam to carry out simulated bomb runs against North Korean targets at a test range in South Korea.

And on Thursday, two B-1s joined Vigilant Ace, a massive aerial drill involving 230 aircraft, 12,000 personnel, and the US’s top stealth jets.

Usually, the US conducts B-1 flights in response to North Korean provocations like missile tests. Usually, North Korea responds with its typically vitriolic propaganda.

For example, after a B-1 flew across North Korea’s maritime border in response to ICBM testing in September, North Korea threatened to shoot down subsequent flights.

But usually, the B-1 flights happen on a nearly one-for-one basis. The back-to-back flights, the inclusion of stealth aircraft, and the massive scope in the drill all point to a marked escalation in tensions just a week after North Korea conducted a surprise test a missile experts say could nuke any US city.