JEONJU -- Eight shots on target were all South Korea needed to score five goals in their first two matches at the FIFA U-20 World Cup on home soil.

South Korea defeated Argentina 2-1 on Tuesday at Jeonju World Cup Stadium in Jeonju, 240 kilometers south of Seoul, to become the first among 24 to clinch a spot in the round of 16. South Korea had four shots on target, and one of the goals came on a penalty converted by Paik Seung-ho. This was after the hosts netted three goals on four shots on target in a 3-0 win over Guinea last Saturday.

Talk about efficiency. And it's been possible because of a dynamic duo in the FC Barcelona system.

Lee Seung-woo of Juvenil A and Paik Seung-ho of Barca B have scored two goals apiece in those two wins. Both of Lee's goals came on great solo efforts, while Paik's first was a result of some deft touch in close range.

The skills and poise displayed by the two youngsters on offense have been nothing short of remarkable. And forward Cho Young-wook, the youngest member of the team at 18, has done yeomen's work up front, banging bodies and creating space for his two talented wingers. It was Cho's fearless play late in the first half on Tuesday that resulted in a penalty for Argentina goalkeeper Franco Petroli -- the two collided in the box trying to get to the ball and Petroli, who got the brunt of the impact, also took the yellow card.

The defensive backs were the unsung heroes of Tuesday's victory. After going with four backs against Guinea, head coach Shin Tae-yong deployed a back three system against Argentina, hoping to tighten space for the skilled Argentines.

It's no small task for any team, let alone a group of under-20 players, to make defensive adjustments from one game to next in a tournament. But these South Koreans had experience in playing in different formations under Shin, who likes to switch his defensive schemes against different opponents, depending on their style of play.

Granted, Argentina led the ball possession 60 percent to 40 percent, and had 19 shot attempts to South Korea's seven. And the South Americans spent the vast majority of the second half in the offensive zone and got their only goal in the 50th, but the South Koreans withstood the pressure and held on for the victory.

On the back line, Jeong Tae-wook, the tallest defender on either team at 195 centimeters, was a physical force. Kim Seung-woo, in his first start of the tournament in the new formation, covered a lot of ground to block Argentina's passing lanes, forcing the opponents to the flanks for weak crosses.

Offensive-minded wing backs, Yoon Jong-gyu and Lee You-hyeon, made some smart passes on offense without compromising their defensive duties.

Once maligned for their lack of cohesion, the defense has kept the opponents to a single goal in two matches so far.

Shin acknowledged that critics aren't too far off in their assessment of South Korea's defense, but he hoped his players changed their perceptions with their display Tuesday.

"I think our defense may appear weak because I am an offensive-minded coach," Shin said. "But if we play like we did today, people will wonder, 'Since when did these guys become so strong on defense?' Our players were determined not to let in a goal tonight. They really made sacrifices and did well."

And perhaps it was because Argentina pushed South Korea around in the second half, but Shin's players visibly tired in crucial late stretches. They were basically running on fumes and goalkeeper Song Bum-keun bailed them out on a couple of occasions.

Shin had been concerned about the young players' conditioning, and it will clearly have to improve if South Korea were to go deeper.

South Korea's best U-20 World Cup performance came 34 years ago in Mexico, where the country made it to the semifinals. Since then, South Korea have made it into the knockout stage five times in 10 tries, while missing the tournament entirely on six occasions. (Yonhap)