Japan has been one of America’s closest allies since the end of World War II, and the two countries have cooperated on several complex diplomatic and military issues. Along with several other allies in the region, Japan and America must contend with the strategic implications of the North Korean nuclear buildup and an increasingly aggressive China. Japan has relied heavily on American presence, support, and technology to protect its national security and bolster its relatively smaller defense forces. In recent years, however, the Japanese government has increased funding for and expanded the scope of the Self-Defense Force.

Three factors have motivated Japanese self-defense policy in the past decade: domestic economic pressure, declining U.S. involvement in the region, and the growth of Chinese hard power. Domestic economic pressure has magnified the effect of the other two factors as public spending increases are across the board and not solely focused on the Japanese Self-Defense Force (JSDF). Declining commitment from the U.S. to regional hard power cooperation under the Trump administration has accelerated the growth rate of the Japanese SDF, although the commitment to JSDF growth predates President Trump. The final factor is the growth of Chinese hard power in the region. This poses a significant, direct, and geographically proximate threat to the safety of the Japanese islands and has been the most influential factor promoting JSDF growth.

The current expansion of the Japanese military is notable for its unprecedented breadth, especially given the historical context. Upon surrendering to the Allied powers at the end of World War II, Japan was occupied by American forces and controlled by General Douglas MacArthur. As part of this generally peaceful occupation, the Japanese Constitution was rewritten under the heavy guidance and influence of the Americans. Chapter 2 of this Constitution renounces the right to wage war and prohibits the government from maintaining land, air, and sea forces. As a result, Japan has created what it calls its “Self-Defence Force.” Among the defining characteristics of this force after World War II were the lack of full-fledged aircraft carriers and the lack of a Marine Corps. Both of these features have changed since Prime Minister Shinzo Abe, who supports militarization, took power in 2012.  In 2018, Japan announced its intent to upgrade two of its flat-top destroyers to aircraft carriers. Flat-top destroyers look similar to aircraft carriers; but are considered defensive based on the fact that they are only able to carry helicopters. These aircraft carriers will be able to operate with newly acquired attack jets such as the American-made F-35. In another move to upgrade the operational capacity of the JSDF, Japan purchased a number of V-22 Osprey Aircraft. These aircraft are significant troop transport weapons, boasting a maximum vertical takeoff gross weight of over 50,000 lbs. The purchase of the V-22s is related to an important development in the JSDF’s land-strike capability: in 2018, Japan activated a unit of marines for the first time since World War II. These marines will be stationed on the island of Kyushu, which is the south-westernmost of the Japanese mainland islands and geographically closest to China. This contingent, called the Amphibious Rapid Deployment Brigade, is made up of 2,100 marines. Its size is a reflection of the government’s goal to create a full force modeled after the power of the region’s most advanced militaries.

The increase in military spending has provoked domestic controversy, including within the Japanese legislature (called the “Diet”). Prime Minister Abe and his Liberal Democratic Party are in favor of the spending hikes. The opposition is fragmented, with the largest representation in the Diet held by the Democratic Party for the People. The arguments against the increase in military spending rely primarily on the illegality of the spending and its economic viability. The language in the Japanese Constitution is unclear as to the difference between a Self-Defence Force and a fully operational military, which has led to robust debate among constitutional scholars. The text of the article in question, Article 9 says that “land, sea, and air forces … will never be maintained.” Abe has called for a constitutional amendment to circumvent the debate. To remain legal for now, the Self-Defence Force is considered an extension of the police and a force only responsible for defense. This explanation has helped maintain strong civilian support in the past, but there has been public backlash amid attempts to expand the SDF through legislation in the Diet. Without a constitutional amendment, Abe’s attempts to continue making the SDF more powerful will face significant political and legal obstacles. 

Even if he is able to win widespread support for his agenda, Abe is constrained by budget precedent. Since World War II, Japan has traditionally limited its military spending to 1 percent of its GDP. Japan currently ranks 8th in the world in military spending, and has increased the defense budget for the past six years in a row. The ruling party is so intent on pursuing its military agenda that it called for a doubling of the defense budget for the FY2019 budget, which would make the Japanese military the third largest in the world by spending. This is in spite of a debt-to-GDP ratio of 253 percent in 2017, which is up from 210 percent in 2009. This is the highest ratio in the entire G20, and more than two times the American ratio of 105 percent in 2017. This will likely become much higher in the long run. Japanese fertility rates are dropping and the population is ageing at one of the fastest rates in the world, causing welfare costs to skyrocket. Abe’s plan to cover these costs is to impose a sales tax hike in 2019. The last time a tax hike of this kind was implemented, in 2014, it contributed to an economic downturn. To offset the economic impact of the tax hike, Japan is increasing spending across the board now. The resulting FY2019 budget plan sets the highest budget in Japanese history at over 900 billion USD. Besides prescient strategic concerns, increased spending on the SDF is partially a function of the general mood for increased spending - which might not have been possible otherwise given the budget constraints. 

Another factor contributing to the rise in JSDF spending is the apparent American turn away from active engagement in the region, marked by increasing tension in the relationship and American demands that Japan pay for more of its own defense. Although Japan and the U.S. have been close political and military allies since the end of World War II, this relationship has not come without disagreements. For the past few years, tensions over continued U.S. military presence on the strategically important island of Okinawa have increased. Even so, the presence is by the continued invitation of the Japanese government. In other words, tangible security benefits are considered to be more important than serious drawbacks such as social tension and high costs. Japan has nevertheless decided to build up its hard power, lowering the demand for American support. A feedback loop could emerge: American demands for Japanese military growth combined with latent tension in the relationship lead to Japanese buildup, further incentivizing America to reduce defense spending in the region and incentivizing continued Japanese military growth. This will increase tension if the two allies do not transition smoothly towards parity -- a vital strategic concern. Besides continuing to support the presence of unpopular American military bases, the Japanese government has consistently expressed its positive attitude towards the relationship. President Trump’s demand that Japan purchase more military equipment from American corporations was initially met with shock and hesitation, but this has subsided. At the end of January 2019, Japan spent over $2 billion on the Aegis Ashore system, America’s formidable missile defense system. This comes on the heels of the Japanese decision to purchase 100 new F-35s -- an increase of 58 from the originally announced plan. So, although recent developments in the relationship between the U.S. and Japan have contributed to the buildup of the Japanese military, the situation is nuanced. There appears to be higher tension in the relationship which is incentivizing militarization, but American involvement in Japanese defense remains robust, suggesting that the magnitude of the effect is limited. 

The third and most important factor affecting Japanese militarization policy is the rise of Chinese military power in the region. It is in Japan’s national interest to counter the powerful and growing threat from Chinese regional aggression. Chinese military spending still outpaces Japan’s: in 2018, China spent three times as much as Japan on the military. Chinese aggression is not just about increasing spending—the country has taken antagonistic actions as well. In 2013, China unilaterally declared an Air Defense Identification Zone (ADIZ) over much of the East China Sea that overlaps with established Japanese airspace. Further, the U.S. advised commercial airlines to respect the new Chinese rules despite an official military rebuke—a sign of Chinese air power in the region. This Chinese policy is in support of its “Anti-Access/Area Denial” (A2/AD) policy, which seeks to restrict foreign intervention and has resulted in heightened military tensions; Japanese government data show a sharp increase in inflammatory naval and aviation activity in contested regions since 2012. This was exacerbated in early 2018 when China surfaced a nuclear submarine near the Diaoyu islands (known by Japan as the Senkaku islands) for the first time. These islands are the subject of shared claims by Japan and China. It is difficult to understate the strength of the message sent by the presence of a nuclear submarine. Modern naval theory holds that the aircraft carrier is the hallmark of hard power, whereas the submarine is a discreet weapon (the American submarine fleet calls itself the Silent Service). It is critically important that submarines remain hidden, because tracking them involves a tedious process using passive SONAR. If the position of the submarine is revealed, then it becomes easier to track that particular submarine during the deployment and in the future. Using a submarine to send an overt message in this way sends a signal of brazen authority and unmatched superiority. In an effort to avoid becoming hopelessly outmatched, Japan has resorted to increasing the size of its Self-Defense Force.

The three factors which have contributed to the recent buildup of the Japanese military are domestic economic pressures, declining commitment from the U.S., and the growth of Chinese military power in the region. If American policy in the future is still committed to avoiding Japanese military buildup on the scale seen in the 1930s, then policymakers must address the implications of the power of the Chinese military.