The United States announced on Monday that it will permanently station attack drones in South Korea in what may be a continuing response to North Korea’s missile launches last week, among other provocations.

The aircraft carrier USS Carl Vinson also joined scheduled exercises with the South Korean navy on Tuesday, prompting the usual North Korean denunciations and threats of retaliation.

The drones headed for South Korea are Gray Eagles, which include significant surveillance upgrades over the famed Predator system. CNN notes Gray Eagle UAVs also integrate with Apache attack helicopters, of which 24 have been deployed to South Korea.

“If North Korea thought they could continue their accelerated pace of weapons testing and deployment without a response, they certainly were wrong,” professor Daniel Pinkston at Troy University in Seoul told CNN. He thought the Foal Eagle exercise was a good time to send the new drones to South Korea, giving Pyongyang (and maybe Beijing) plenty to think about. The United States does not typically announce such drone deployments to the public.

Another interesting theory CNN mentions is that the United States wants to shore up South Korea’s resolve in the face of a political crisis and encourage the successor to impeached President Park Geun-hye not to back out of deploying the THAAD missile shield. Park’s most likely successor, Moon Jae-in, tends to favor improving relations with North Korea. A swarm of balloons reading “No THAAD! Yes Peace!” was flown over an impeachment rally on Saturday.

The Foal Eagle exercise Professor Pinkston referred to involves the Carl Vinson battle group taking up a position east of the Korean peninsula and launching F-18 fighter jets.

CNN reports North Korean state media denounced Carl Vinson’s arrival as a “reckless scheme” to set up a sneak attack and warned the North Korean military will “launch merciless ultra-precision strikes from ground, air, sea and underwater” if the Foal Eagle exercise infringes on Pyongyang’s “sovereignty and dignity.”

North Korea continued its charm offensive on Tuesday by blaming the U.S. and South Korea for the death of Kim Jong-nam, half-brother of dictator Kim Jong-un, who died in Malaysia last month due to complications from having a weapon of mass destruction smeared on his face.

At a news conference, North Korean Deputy U.N. Ambassador Kim In-ryong said of Kim Jong-nam’s death: “From A to Z, this case is the product of reckless moves of the United States and South Korean authorities.”

He darkly speculated that the United States is one of the few nations that can produce VX nerve agent, named by Malaysian authorities as the murder weapon, and portrayed the assassination as part of a U.S. plot to “store up international repugnancy toward the DPRK.”

Deputy Ambassador Kim said the U.S. and South Korea are using “political chicanery” to bring down the North Korean government, and if that doesn’t work, they want “nuclear war against the DPRK at any cost.” He said the Foal Eagle military exercise was just a dry run for the “real war” to come.

The North Korean delegation to the U.N. followed up with a declaration that Pyongyang will never abandon its nuclear weapons program. Voice of America News quotes experts who say North Korea could be less than four years away from developing a miniaturized nuclear warhead that can be mounted on a long-range missile capable of reaching the continental United States.