President Moon Jae-in inspected the weapons and troops at the headquarters of the Navy's Second Fleet in Pyeongtaek, 70 kilometers south of Seoul.
It was the first time for the country's official Armed Forces Day ceremony to be held at a naval base, as it is usually staged at the Gyeryongdae military complex in South Chungcheong Province.
For the celebration of the 65th anniversary in 2013, a massive military parade was held at the Air Force's Seoul Airport.
The Second Fleet is in charge of defending South Korea's western waters just south of the Northern Limit Line (NLL), the de facto inter-Korean sea border.
The two Koreas have engaged in several deadly naval skirmishes in waters close to the NLL.
The choice of venue for this year's event reflects the Moon administration's resolve to deal sternly with the North's provocations, defense officials said.
Among the "strategic" weapons on display at the ceremony were Hyunmoo-2 ballistic missiles and Hyunmoo-3 cruise missiles. The military put its latest Hyunmoo-2C missile, which has a range of 800 kilometers, on public show for the first time.
The missiles are key elements of South Korea's ongoing "three-axis" defense platform, which consists of the Kill Chain pre-emptive strike system, the Korean Air and Missile Defense (KAMD) and the Korea Massive Punishment and Retaliation (KMPR) scheme.
Also shown were the Army Tactical Missile System (ATACMS), the Hyungung anti-tank guided weapon, Patriot PAC-II air defense missiles and M-SAM surface-to-air missiles, as well as Taurus and SLAM-ER air-to-ground missiles.
In a speech, Defense Minister Song Young-moo pledged every effort for defense reform.
He said it's the "calling of the time to nurture a strong military as agile as a leopard that is capable of overwhelming any enemy threats and defending ourselves through defense reform."
The ceremony was attended by thousands of people and broadcast live nationwide.
The South's Armed Forces Day falls on Oct. 1 and commemorates the day in 1950 when the South's forces broke through the 38th parallel border line during the war against the invading North.
But this year's ceremony took place early, with Koreans scheduled to enjoy the Chuseok holidays next week.
Meanwhile, Gen. Vincent K. Brooks, the commander of U.S. Forces Korea, was awarded the Tongil Medal, South Korea's top national security merit, for his dedicated service here, source from the Yonhap.
