Missile crisis: A timeline of North Korea's recent launches

North Korea's latest in a series of provocative actions is a challenge to both the United States and South Korea, military officials say.

Monday's ballistic missile test is the ninth such action this year.

Here is a look at the key developments that helped give rise to the latest crisis:

Donald Trump inaugurated as U.S. president.

North Korea tested a new midrange ballistic missile, the Pukguksong-2. The country said the missile uses solid fuel, an advance that increases a weapon's mobility and makes it harder for outsiders to detect a coming launch.

North Korea fired four ballistic missiles that flew about 1,000 kilometers (620 miles). Three landed in waters near Japan. The country later said it was simulating nuclear strikes on U.S. military bases in Japan.

North Korea fired a missile on the eve of a meeting between Trump and Chinese President Xi Jinping. The missile flew about 60 kilometers (40 miles) before falling into the sea.

North Korea fired a missile off its east coast, but the launch apparently failed. U.S. officials said the missile was likely a KN-17, a new Scud-type missile.

South Korean and U.S. officials said a North Korean midrange ballistic missile, presumably a KN-17, failed shortly after launch.

Trump called North Korean leader Kim Jong Un "a pretty smart cookie" in a U.S. television interview for being able to hold onto power after taking over at a young age.

Liberal Moon Jae-in was inaugurated as South Korea's president. He said he wants to improve ties with North Korea.

North Korea test-fired its newly developed Hwasong-12 missile, which it said can carry a heavy nuclear warhead. Outsiders saw the launch as a major step forward because of the height it reached. Moon expresses deep regret over the launch.

North Korea again tested the solid-fuel Pukguksong-2. The missile flew about 500 kilometers (310 miles) before falling into the ocean.

Moon's government said it will allow a South Korean civic group to contact North Korea to help fight malaria. This is the first government approval of a cross-border civilian exchange since January 2016.

South Korean and Japanese officials said North Korea fired a short-range ballistic missile that landed in Japan's maritime economic zone.

North Korea fired several missiles, believed to be anti-ship missiles, into the Sea of Japan.

North Korea tested a new rocket engine that some believe could be fitted to an intercontinental ballistic missile.

The nation's first intercontinental ballistic missile named Hwasong-14 was tested during a launch from Panghyon Aircraft Factory, and landed 37 minutes later into Japan's exclusive economic zone. Authorities said the missile could possible reach Alaska, Hawaii, or even Seattle if it was aiming long.

The 14th missile test brought word of North Korea's ability to possibly strike Los Angeles, Denver, Chicago, Boston or New York. The missile landed near the northernmost Japanese island of Hokkaido.

North Korea may have successfully produced a miniaturized nuclear warhead that can fit inside its missiles, a Japanese defense paper and U.S. media report said. If the claim is substantiated, it would be a key benchmark in the country's attempt to become a full-fledged nuclear power.

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