Propaganda in Korea has been ongoing since the war. These days, both sides have loudspeakers that broadcast across the DMZ. Southern speakers play things as simple as the news and weather reports. The south knows that people in the north are listening because when they say that it will rain, they can see people bringing in their laundry from the line.

As for your particular pieces; the first one is a piece that was given to people in the south. The front is self explanatory and the back is a translation written in Korean. It's written in the older style, top to bottom, left to right, and heavy on the Hanja (Chinese characters). My Hanja skills are limited to days of the week and food portion sizes, so I'm pretty lost on most of it, but even the Hangul has some words that don't directly translate to what's on the front, so "translation" may not be the best way to describe it as much as "general gist" of it.

The second piece is much more interesting, IMO. On the front, it has English and Korean. This time, the Korean is written entirely in Hangul with no Hanja and it's written left to right, top to bottom, as it is today. On the back is a warning to the North Koreans. The Korean is here (mainly so i don't have to retype it if I want to check it again!)

까지 책임을 추궁할 것이다.

도록 허가 하거나, 명령 하는 자에 대하여서는 나 는 끛 흑은 이 원측에서 버서나는원인을만들거나, 버서나거나 말하노니 북한측을위아여, 이 원측에서 버서나거나, 내 지휘하에 잇는 모든 군 대의 총 사령 관으로써 나는 유엔 안전보장 이사회 가 채택 한 결의에 의하여 것이다.

군에게 포착 될 때에도 역시 동 일한 대우를 하여야 할에참가한 다른 나라 군인이 언때를 막론 하고 북한 한국전루에 이서서 우리 미국군 은 물론 미국댕발것이다.

채용하고 승인한 인돚의적 제원측으로 그네들을 군은 군사 분쟁에관하여 믄명 국가들이 군대에게 포착되거나 혹은 구류 되어잇는 북한 대한전루에 잇서서 현재 대가 작전지휘하고잇는.

맥아더 장군의포고

And the rough translation is:

We will prosecute war crimes. I will go after anybody on either side for committing war crimes. I am committed to the UN resolution. When captured by the enemy, US soldiers should be treated humanely. The military is conducting operations in the north (?).

MacArthur's Declaration

I'm not entirely sure on the last sentence, but I think it's accurate. I'll check with someone on that tonight.

This leaflet would have been used in the immediate onset of the war. The North Koreans had executed captured POWs and committed massacres against soldiers and civilians alike. The message tells the soldiers that they will be prosecuted for war crimes and that all POW's should be treated well. Not too long after the beginning of the war, the war crimes stopped. The North Korean claim is that it was some rogue commanders in the field who had committed them and it wasn't North Korean policy.

As far as the broader development and impact, there's a lot of information out there about them. Take a look at the National Museum of the US Air Force and their display on Korean War propaganda.. There were political papers about Kim Il-sung and how the communists were wrong, information about bombs and targets to warn civilians, and leaflets for soldiers to encourage them to surrender. North Korean and Chinese propaganda was similar. The Chinese propaganda frequently asked why the UN soldiers were in Korea instead of home and pointed out that if they just left, the war would end.

You can see the evolution of the leaflets. At first, everything is written in Korean but then Chinese appears. The Chinese put their own name on their Christmas card in 1951 despite entering the war in secret a year earlier (seriously, that is a NICE card though!) You can also see the names changing - MacArthur, Ridgway, Clark, and Van Fleet.

Success would be measured in different ways. One operation, Operation Moolah, was a campaign to get a MiG fighter plane. The US dropped leaflets offering $50,000 for anyone who brought a MiG-15 to the south plus an additional $50,000 for the first person to do so. The leaflets were dropped over the Yalu River area where the MiG bases were located. It was reported that for the next 8 days, no MiGs were seen flying. The speculation was that the communist forces were screening the pilots for politically unreliable ones, but weather could have been a factor. Further, from that point on, a radio jammer prevented American broadcasts in Russian from the area, but the Chinese and Korean broadcasts were unmolested. The conclusion is that the Russians, who had built the MiG, were concerned. Operation Moolah didn't work before the end of the war, but in September, No Kum-suk defected with his MiG, unaware of Operation Moolah. He took the money and settled in the US. Check out his book "A MiG-15 to Freedom" for more information.