President Barack Obama visited US troops in the Demilitarised Zone (DMZ) that separates the two Koreas on Sunday.
Obama arrived in South Korea to participate in the two-day global security meet on nuclear weapons that begins on Monday.
After reaching Seoul, Obama immediately flew to the DMZ in military helicopter and met over 20,000 US troops stationed there.
The US president also surveyed the highly fortified North Korea border about ten minutes from a viewing platform behind the bullet proof enclosures.
"You guys are at freedom's frontier," Obama told the US troops at the DMZ.
Take a look at Obama at the Korean border: