U.S. Forces Korea finished moving key components of the THAAD battery -- including a radar module and a number of mobile launch systems -- into the deployment site in Seongju County, some 200 kilometers south of Seoul, at around midnight on Wednesday.
The convoy was met by hundreds of Seongju residents, concerned about the system's potential environmental impact, who tried to block their path -- but to no avail.
The THAAD system will now undergo several localization tests before becoming fully operational with the help of incoming components.
The move, which signals that the deployment is underway, comes just six days after a crucial land-transfer agreement that was signed by the two nations.
The news came as a surprise to many,. as South Korea's defense ministry had said just last week that any significant progress would only begin after a thorough environmental impact analysis, which they anticipated could take months.
"Based on the way things are developing, we've determined that the deployment will not be finished in a short period of time."
But it now appears that the ministry has reversed itself somewhat.
"Regarding the U.S. military's decision to expedite the deployment, the defense ministry said that it will still conduct small-scale environmental tests in the region as the deployment proceeds."
Observers and Korean media outlets have speculated that the early deployment is being carried out to minimize the possibility of the deployment decision being overturned or delayed by the next incoming president.
Meanwhile, the arrival of the components prompted China to renew its objections to the system.
China's foreign ministry on Wednesday urged South Korea and the U.S. to withdraw the system, as it will only bring more instability to the Korean Peninsula.
Kim Jung-soo, Arirang News.