Less than a year after Senate confirmation of Caroline Kennedy, rising tensions between Japan and China have made her job one of the most important on the planet.

Last November, the daughter of the late President John F. Kennedy rode in an ornate, horse-drawn carriage through the heart of Tokyo to Japan’s Imperial Palace. The new United States Ambassador to Japan, as dictated by tradition, presented her credentials to Emperor Akihito, Japan’s reigning monarch. (The previous day, she had presented herself to the government of Prime Minister Shinzo Abe.)

America’s Japan posting had become a quiet one. Two decades after the end of the Cold War, the posting had become less important to a post-9/11 Washington. After a long string of veteran politicians and diplomats who could shrewdly manage both the bilateral trade relationship and the U.S.-Japan security alliance, the previous ambassador had been a major donor to the Obama campaign.

A subsequent chill in relations between Japan and its neighbors South Korea and China has made Kennedy’s job a whole lot tougher. She must reassure Japan that the American pivot to Asia is real, despite a lack of tangible commitment. Complicating matters is an assertive crowd of Japanese right-wing politicians who constantly anger Japan’s neighbors with their desire to amend the Japanese constitution and their occasional historically insensitive comments. The carriage that brought Kennedy to the Imperial Palace has turned into a pumpkin and she finds herself representing the United States in the middle of the biggest crisis to hit Asia since the end of the Vietnam War.

The United States, anticipating a post-Afghanistan war era, is turning its attention to Asia in a so-called “Pacific Pivot.” Many of China’s neighbors, particularly the Philippines, Vietnam, and Japan object to China’s territorial demands, which include virtually the entire South China Sea and the Japanese-held Senkaku Islands. The United States has said that it will rebalance its forces away from the Middle East to Asia, but relatively little in terms of real redeployments has taken place. This week’s visit by President Obama to Asia will seek to convince regional allies, particularly Japan, that the pivot is real.

And Japan certainly needs reassuring. Buffeted by decades of economic stagnation and having ceded the position of second-largest economy in the world to its rival, China, Japan’s position has been in relative decline for years. Tokyo recognizes the 1960 U.S.-Japan Treaty of Mutual Cooperation and Security as its No. 1 strategic alliance, but watched in dismay as America became fixated on the Middle East. At the same time, just across the East China Sea, China has embarked on a lengthy modernization and buildup of the People’s Liberation Army.

An increasingly aggressive China laid claim to a small, uninhabited chain of islands off China’s central coastline. The Senkaku Islands, known as the Diaoyu Islands in China, are claimed by both countries and have been the scene of numerous confrontations. Japan is worried that China might try to seize the islands, either overtly or through the use of “activists” such as in Ukraine, and is eager to secure American support in defending them.

In response to the situation with China, Japan’s new right-wing leadership is taking the opportunity to push through long-envisioned reforms to the national constitution. Japan’s constitution prohibits the use of war as an instrument of national policy and recognizes only the nation’s right to self-defense. Prime Minister Shinzo Abe would like to amend that to include “collective self-defense”: that is, the ability to defend Japan’s allies as an important milestone toward Japan having a “normal” military capable of both offensive and defensive action.

The United States approves of efforts to normalize Japan’s military as beneficial to the U.S.-Japan alliance, which enjoys a comfortable margin of approval in both countries. The reforms, however, come with a price: The Japanese politicians pushing them have a tendency to anger Japan’s neighbors with offensive statements about Japan’s involvement in World War II.

The Obama visit is an important display of solidarity, but once he leaves, Caroline Kennedy will be left to handle Tokyo. Corey Wallace, a lecturer at the University of Auckland, New Zealand and former policy adviser for the Japanese government, told The Daily Beast “[Kennedy] has had to deal with a lot in terms of not only being called upon to communicate U.S. policy positions regarding the management of territorial and strategy issues between Japan and China, but management of the alliance.”

The main source of regional anger has been repeated visits by members of the Abe cabinet, including Abe himself, to Yasukuni, a shrine in Tokyo devoted to those who died in the Emperor’s service. The shrine contains the names of more than 1,000 war criminals, including 14 Class A war criminals—the worst of the worst. The enshrinement of such individuals, and the implicit act of honoring them with visits by government officials, infuriates China and South Korea, two countries who suffered the most of Japan’s wartime depredations. Justin Bieber was forced to apologize for his visit to the shrine this week.

In an interview with Japan’s public broadcast network NHK, Kennedy alluded to the Abe visit, saying, “I think anything that distracts from all the positive work that we do together and makes the regional climate more difficult is something that is not as constructive moving forward, because we really need to keep looking forward."

The message to Japan’s leadership was clear: cut out the visits. But in the wake of Kennedy’s rebuke the visits from members of the Abe administration have continued. Wallace says they are ”not just directed at China and Korea and their view of history, but also a direct challenge to the U.S. itself in terms of its ability to dictate how Japan manages its own domestic issues and how it approaches China and Korea in particular.”

What looked like a quiet ambassadorial posting in early 2013 when the Kennedy appointment was floated with Tokyo has turned into something else entirely. Not only must Caroline Kennedy navigate the U.S.-Japan alliance through an unfolding confrontation with China, she must deal with recalcitrant Japanese officials while keeping eye on American relations with China and South Korea. The days of Japan as a quiet posting are over.