SEOUL (CNN) -- The first pieces of a US-built missile defense system designed to mitigate the threat of North Korean missiles arrived at the Osan Air Base in South Korea Monday night, according to the US military.
The announcement comes just a day after North Korea test-fired four ballistic missiles into the Sea of Japan, also known as the East Sea.
With North Korea upping the amount of missile and nuclear tests last year, the US and South Korea have publicly stressed the need to speed up the deployment of the technology, which is called the Terminal High Altitude Area Defense (THAAD) system.
It's designed to shoot down incoming missiles that threaten civilian populations, akin to shooting a bullet with another bullet, experts say.
"Continued provocative actions by North Korea, to include yesterday's launch of multiple missiles, only confirm the prudence of our alliance decision last year to deploy THAAD to South Korea," Adm. Harry Harris, commander, US Pacific Command, said in a news release.
US Secretary of Defense James Mattis and South Korean Defense Secretary Han Min-koo spoke over the phone last week and agreed that THAAD should be deployed "ASAP."
North Korea sees the missile defense system as a threat that will push the Korean peninsula to the "brink of a nuclear war," it said last month through state media.
The US and its allies in the region, notably South Korea and Japan, tend to focus on THAAD's defensive nature. They tout its value as a system to prevent a missile from hitting a target and killing people.
"This is purely a defensive measure that the alliance must take in light of the serious threat posed by North Korean missiles," Chris Bush, a spokesman for the US Forces in Korea said.
But Beijing and Moscow don't see it that way. They're both vehemently opposed to THAAD's deployment because they believe it threatens their own security interests.
CNN's Paula Hancocks reported from Seoul, while Joshua Berlinger reported and wrote from Hong Kong
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