Barely nine months in power, Japan’s prime minister Yukio Hatoyama announced his resignation today. Hatoyama led Japan’s main opposition party, the Democrats, to electoral victory in August 2009, defeating the traditional governing party the Liberal Democrats at the time. He promised tax cuts and a new approach to foreign policy but proved unable to cope with Japan’s lingering economic trouble.

Hatoyama cited his inability to convince the Americans to move a Marine base off the island of Okinawa as reason for his resignation. Some 4,000 US Marines are stationed on the crowded island amid growing discontent from the local population.

Western media were quick to report on the tension that emerged between Japan and the United States in January over the Marine presence. Relations between the two countries have been fairly stable since the end of World War II. Hatoyama repeatedly suggested on the campaign trail that he would push for the relocation of the base but last week gave in and accepted the existing arrangement.

At World Politics Review, David Axe notes that the Okinawa base is “part of a constellation of American bases that buttress Japan — and indeed all of East Asia — against a rising tide of Chinese military power and escalating tensions on the Korean Peninsula.” In spite of Hatoyama’s intention to conduct a foreign policy more independent of the United States, even he may have had to admit that Japan fares well under the protective umbrella of American might. Unfortunately for him, “that meant breaking a campaign promise,” according to Axe, “and ultimately torpedoing his own government.”

There may have been a little more to it though. As Kyle Mizokami writes at Japan Security Watch, the prime minister’s polling rating had plummeted in recent months to an unprecedented low of just 17 percent — “so low in America they would not be allowed to buy alcohol.” His failure to live up to one of his campaign promises was his ultimate undoing, knows Mizokami, “but his indecisiveness, naivete, lack of leadership skills, inability to manage his cabinet, and general incompetence all played a role.”

The prime minister shot himself in the foot right by allowing the Okinawa base issue to dominate his political agenda. “Hatoyama clearly started to grapple with something he did not fully understand, only to realize too late his mistake.”

His awkward political maneuvering did not go unnoticed in his own party. Behind the screens Ichirō Ozawa, secretary general of the Democratic Party of Japan, was pushing the government to abandon another one of its campaign promises: to cut petrol taxes. Just months after the Democrats took office, Ozawa forced the country’s finance minister to step down in favor of his ally Naoto Kan. Hatoyama wasn’t pulling the strings. The discord culminated last week when a minority left-wing party aligned with the Democrats split from the ruling coalition.

For the country’s economy, Hatoyama’s resignation may turn out to be a blessing or a curse. Contrary to the more conservative Liberal Democrats, his party favored reform, greater personal responsibility and a more flexible market. But last December it became obvious that the Democrats intended to distance themselves from the free-market policies of former Prime Minister Junichiro Koizumi. Over Christmas they approved a record trillion dollar budget which, according to The New York Times, “encompasse[d] ambitious welfare outlays to help households cope with the country’s deep economic woes.” The paper warned though that “the scale of new spending could renew investor jitters about the government’s burgeoning debt.” To what extent this was Hatoyama’s policy or that of party leader Ozawa, who also stepped down on Wednesday, we are bound to find out depending on who will displace the former.

Because Japan has a parliamentary system, no elections are called for to elect Hatoyama’s successor. Upper house elections are scheduled to take place in July however. Hatoyama’s resignation may be an attempt on the part of the Democrats to boost their waning popularity. Ozawa-appointee Naoto Kan, currently serving as finance minister, is rumored to succeed him.