South Korea threatened on Tuesday to restart anti-Pyongyang frontline propaganda broadcasts, the latest escalation in a Cold War-style campaign between the two nations. This follows North Korea’s resumption of trash-carrying balloon launches across the border.

On Monday night, North Korea sent huge balloons carrying plastic bags of rubbish across the border, marking its fifth such campaign since late May. This appears to be a response to South Korean activists flying political leaflets via balloons.

In a speech delivered on Tuesday to mark the Korean War anniversary, South Korean President Yoon Suk Yeol denounced North Korea’s balloon activities as “a despicable and irrational provocation.” He emphasized South Korea’s commitment to maintaining a strong military readiness to counter any provocations from North Korea.

Later on Tuesday, Yoon boarded a visiting U.S. aircraft carrier docked at a southeastern port. Addressing American and South Korean troops, he asserted that the alliance between the two countries is the world’s strongest and capable of defeating any adversary. This marked the first time a sitting South Korean president has boarded a U.S. aircraft carrier since 1994.

South Korea’s military reported that North Korea launched approximately 350 balloons in its latest campaign. Around 100 of these landed on South Korean soil, primarily in Seoul and surrounding areas, which are located about 25–30 miles from the border. The military confirmed that the trash carried by the North Korean balloons consisted mainly of paper and no hazardous materials were found.

In previous balloon launches, North Korea had dropped manure, cigarette butts, waste batteries, along with cloth scraps and waste paper in various parts of South Korea. While there were no reports of major damage, South Korea responded by redeploying giant loudspeakers along the border on June 9, marking the first time in six years, and briefly resumed anti-North Korean propaganda broadcasts.

Joint Chiefs of Staff spokesperson Lee Sung Joon informed reporters on Tuesday that the South Korean military is prepared to reactivate its border loudspeakers. A written statement from the Joint Chiefs of Staff indicated that officials would assess unspecified strategic and operational circumstances, and the resumption of broadcasts would depend on North Korea’s actions.

Balloon launches and loudspeaker broadcasts were prominent psychological warfare tactics employed by both Koreas during the Cold War. While both sides had agreed to cease such activities in recent years, they have occasionally resumed them when tensions rise.

North Korea exhibits extreme sensitivity to South Korean border broadcasts and civilian leafleting campaigns, as it restricts most of its 26 million citizens from accessing foreign news.

Civilian activist leafleting campaigns, mainly conducted by North Korean defectors, involve distributing leaflets critical of North Korea’s human rights violations and USB sticks containing South Korean TV dramas. Past South Korean border broadcasts have included K-pop songs, weather forecasts, and external news. In a statement released on Friday, Kim Yo Jong, the powerful sister of North Korean leader , labeled them “human scum” and “disgusting defectors.”

South Korean officials maintain that they do not restrict activists from sending leaflets to North Korea. This aligns with a 2023 constitutional court ruling that overturned a law criminalizing leafleting, deeming it a violation of free speech.

Many experts believe that the North Korean balloon campaign is likely intended to intensify debate in South Korea over civilian leafleting and create a broader internal division.

Concerns regarding North Korea intensified in mid-June when North Korean leader Kim Jong Un and Russian President Vladimir Putin signed an agreement that requires each country to provide aid if attacked and pledges to strengthen other forms of cooperation. Observers view this accord as the strongest connection between the two countries since the end of the Cold War.

The United States and its allies believe that North Korea has been supplying Russia with vital conventional arms for its war in Ukraine in exchange for military and economic assistance.

In his Korean War speech, Yoon described the Kim-Putin deal as “anachronistic.” South Korea, the U.S., and Japan issued a joint statement on Monday forcefully condemning the expansion of military cooperation between Russia and North Korea.

The arrival of the USS Theodore Roosevelt carrier and its strike group is intended to address nuclear threats and North Korea’s escalating military partnerships with Russia, according to South Korean officials. Their deployment also aligns with a 2023 South Korea-U.S. agreement aimed at enhancing the “regular visibility” of U.S. strategic assets on the Korean Peninsula.

Yoon announced that the U.S. carrier is scheduled to depart the South Korean port on Wednesday for a new trilateral South Korea-U.S.-Japan drill. The new multidomain “Freedom Edge” exercise is designed to sharpen the countries’ combined response capabilities in various operational domains, including air, sea, and cyberspace.

North Korea has previously responded to such major U.S.-led drills with missile tests. On Monday, Kim Kang Il, North Korea’s vice defense minister, characterized the deployment of the USS Theodore Roosevelt as “the reckless option and action of the U.S.”