Trump's 25% High Tariff Letter, Ally or Threat?

Trump's High Tariff Letter and Diplomatic Implications

In July 2025, former U.S. President Donald Trump sent a letter unilaterally notifying South Korea and Japan of a 25% high tariff, causing a significant ripple in the Northeast Asian diplomatic landscape. This action is interpreted not merely as a trade policy or economic pressure, but as a diplomatic event testing the alliance. Particularly noteworthy is the fact that the content sent to both countries was nearly identical, and the publicity channel was Trump's personal social media rather than traditional diplomatic channels, marking the tariff letter as a political message that transcended 'normal diplomacy.' It is highly relevant to explore why Trump targeted South Korea and Japan simultaneously at this point, how Japan's Ishiba administration perceived it, and what strategy South Korea should adopt in response. This article aims to examine the intent and implications of the tariff letter, the role of alliances, and the direction of sovereign diplomatic strategies centered around these three key questions.

The Reality of Trump's Tariff Letter: Diplomacy or Threat?

The letter sent by former President Trump in early July 2025 to the South Korean and Japanese governments imposing a 25% tariff was not a simple trade measure. Through his social media, he effectively declared a "conditional threat," explicitly naming the leaders of both countries. Furthermore, the content of the letter was nearly identical, and the posting times were just a minute apart, indicating a lack of diplomatic courtesy and genuine willingness to negotiate. This approach is markedly different from established international diplomatic practices. Communications between heads of state are typically conveyed confidentially through diplomatic channels and result from coordination based on mutual trust between the two countries. However, this letter came close to being a unilateral notification from Trump, appearing to be a political performance aimed at showing he still wields influence on the international stage. Trump is exploiting the essence of military alliances through this letter. South Korea and Japan have maintained security cooperation with the United States for a long time, particularly accepting U.S. demands regarding troop presence and defense cost-sharing, which has a historical backdrop. Trump views this as a "weakness" and is employing a strategy that links tariff increases to defense cost negotiations, thereby exerting pressure on both the economic and security fronts. In other words, he is creating a binary choice structure of "either increase defense spending, or bear the tariffs." This approach does not align with the traditional U.S. foreign policy framework of "values-based alliance diplomacy" and is a prime example of Trump's unilateral, transactional diplomacy. Notably, at the BRICS summit, a statement was adopted that directly criticized this approach, with Brazil's President Lula strongly denouncing that "the president of a major country threatening the world via social media is a retrograde act." In this way, Trump’s tariff letter is gradually losing diplomatic legitimacy in the international community.

Japan's response: The practical calculations of the Ishiba administration

Japan is showing a relatively swift and strong stance regarding Trump's tariff letter. Prime Minister Kishida expressed regret, stating that the US demand is "an insult to allies," and both the Japanese media and political circles are rallying behind the government's firm response. This reaction is based not just on diplomatic fervor but also on domestic political schedules and strategic judgments. The most important factor is the House of Councillors election scheduled for July 20. The ruling Liberal Democratic Party seeks to firmly establish its political leadership through this election, and Prime Minister Kishida is adopting a strategy to rally support based on the theme of "independent diplomacy." Trump's tariff letter is, in fact, being leveraged as an opportunity to stimulate anti-American sentiment and strengthen domestic public opinion. Interestingly, Trump appears to have taken this into account as well. By postponing the tariff implementation date from July 9 to August 1, he has left room for negotiations after the election. This is interpreted as a strategy that Trump intentionally coordinated while considering Japan's political schedule. Thus, in a situation where both political calculations align, Trump is responding with a card of "pressure," while Kishida counters with a card of "resistance." Additionally, Japan is preparing substantial "countermeasures" such as selling government bonds, refusing to import American rice, and not opening the automotive market. Particularly, the opening of agricultural markets is a sensitive issue for conservative supporters in Japan, making it difficult to accept Trump's demands. The Japanese government is confronting US demands head-on, emphasizing food security issues and effectively communicating its position to the international community. This response is seen as an attempt to break away from the past notion that "US requests = automatic acceptance," and to reclaim its position as an equal partner.

South Korea's Response: Is it a Key Player in Diplomacy or a Bystander?

South Korea is also one of the countries that received a letter from Trump regarding tariffs and has been informed of nearly identical content as Japan. However, there is a significant difference in the response approach. While Japan strongly protested and officially used the term "regret," the response from the South Korean government appears relatively cautious and passive. The issue is also evident in the attitude of the media and public opinion. Major domestic media are treating this matter as a simple report, without making any clear comments or raising concerns. This seems to be a combination of unnecessary intimidation towards Trump and a unilateral following sentiment towards the United States. Experts point out that this is a time when the media should not be a bystander in diplomacy but should take an active role. The request for a ninefold increase in defense costs demanded by Trump is essentially a demand akin to surrendering sovereignty. What is needed to transform this into diplomatic negotiations is not only the technical response of the Trade Negotiation Headquarters but also a strong backlash from public opinion and a change in the landscape of public sentiment. Canada faced Trump's unreasonable demands and gained national support, ultimately achieving success in both elections and trade. Japan is also referring to this precedent. In contrast, South Korea still perceives the United States as an "absolute elder state," and some conservative media maintain an attitude of "we must follow because the U.S. wants it." However, the international situation can no longer be navigated through such a subordinate perception. Trump has already experienced multiple defeats in negotiations with Canada, Mexico, the EU, India, and China and has identified South Korea and Japan as the countries that are most likely to "listen well" again this time. In this situation, the strategy South Korea should adopt is clear. First, it must formalize a joint response with Japan to block Trump's divide-and-conquer strategy. Second, the media and public opinion should recognize their role as a "rear support" for negotiations and convey a clear message. Third, the negotiation team must ensure that they respond based on national support and remember that unilateral concessions can lead to results detrimental to national interests.

Conclusion: Responsibilities as a Subject of Diplomacy

Trump's tariff letter clearly demonstrates how easily diplomatic relations conducted under the name of 'alliances' can be threatened. Japan has chosen a hardline response that reflects the realities of its domestic politics and is employing a strategy to secure leadership in its diplomacy with the United States. In contrast, South Korea has yet to take sufficiently proactive measures, which poses a risk of being perceived as a weak negotiator in the international community. Diplomacy is not merely the responsibility of negotiation teams. Media, public opinion, and citizens' perceptions are core variables that determine a nation's negotiating power. Now is the time to move beyond the perspective of onlookers and fulfill our respective responsibilities and roles as active participants in diplomacy. Responding to Trump's demands is not just a trade issue it is a matter of protecting the sovereignty and dignity of the Republic of Korea. We are at a crossroads right now. Should we continue as a dependent ally, or should we forge a path as a dignified diplomatic partner? The answer to this question hinges on the attitudes of our citizens and government at this very moment. An alliance is not a relationship that threatens by targeting weaknesses it is a promise to stand together. We must now demonstrate through our actions whether we will uphold the true meaning of that promise.