In September, the upper house of Japan’s National Diet approved legislation already passed by the lower house that, for the first time since 1945, would let Japanese troops fight overseas. Far from signaling the start of larger changes to the country’s long-standing pacifist position, however, the legislation stirred up impassioned opposition—especially opposition from unexpected sources. This may very well be the high-water mark from which Prime Minister Abe’s intention to reform Japan’s defense program recedes.

Demographics, it turns out, provide an unexpected explanation to the backlash against the national security legislation and the sudden turnaround in public backing for the Abe administration. Throughout the summer of 2015 thousands gathered in protest around the National Diet building calling for Abe’s resignation and an end to security bills that they believe could eventually entangle Japan into a war of someone else’s doing. Many of the protests were spearheaded by proactive youth—previously seen as apathetic to political issues—hearkening back to the 1960s student demonstrations against the U.S.-Japanese security treaty. Those protests ironically occurred under the premiership of Nobusuke Kishi, Abe’s grandfather, who was forced to resign.

Undeniably, explanations coming from Abe’s administration were poor, doing little to assuage the people’s concern. Furthermore, public distrust escalated when, despite media surveys confirming that an overwhelming majority of the constitutional-law scholars believe the bills to be unconstitutional, the legislation was pushed through parliament. Abe’s statements from his first spell as prime minister in 2007, declaring that he intends to usher in a “departure from the postwar regime,” have also added to the impression that the security bills are revolutionary. In reality, however, the legislation is no more than evolutionary.

Abe has no intention of departing from Japan’s pacifist stance. Yet, he firmly believes that Japan must overcome “one-country pacifism” in order to meet the demands of the post-Cold War security environment and to strengthen the U.S.-Japan alliance in light of growing tensions in the Asia-Pacific. The deficiencies of the “one-country pacifist” model were exposed in 1991 by what came to be known as the “Gulf War trauma.” Self-imposed laws prohibited Japan from supporting the U.S.-led coalition by sending its Self-Defense Forces (SDF) overseas. Japan could do little to contribute beyond checkbook diplomacy, and faced stern criticism from the international community. It was a salient “teachable moment” that served as a wake-up call to Japanese policy makers of the necessity for new thinking with respect to their country’s participation in international security. The recently passed legislation seeks to redress the limitations of the “exclusively defensive” policy by giving Japan the legal right to collective self-defense and an expanded overseas role for the SDF. In other words, Abe is simply attempting to shift Japan’s defense policy from a “passive” view of pacifism to “proactive pacifism.” However, attempts to reassure the public that this shift is no radical departure from pacifism have been fundamentally undermined by the hidden hand of demographic pressures that are starting to take their toll, giving rise to a form of “silver pacifism” in Japan.

First, support for the security bills was lowest amongst Japan’s pensioners—only 19 percent according to an Asahi Shimbun poll. For this generation that remembers World War II and grew up in the postwar era, Article 9 of the constitution forms a core part of their identity. They assert it was this dedication to pacifism that has secured seventy years of peace, providing the very foundation for Japan’s postwar miracle growth. For them, naturally, any deviation from this would jeopardize Japan’s future security and prosperity. Resisting the bills has been something of a swan song for this generation that has little time left to bequeath Japan’s postwar legacy of pacifism to future generations.

Next, expanding the role of the SDF costs money in equipment, joint military exercises and personnel. Japan, however, faces inevitable budgetary constraints brought about by a shrinking tax base. Belying reports of Japan’s “record-breaking” defense budget under the Abe administration, defense spending remains at 5 percent of the national budget (and 1 percent of GDP). The large elderly electorate is Japan’s most powerful constituency, one with a vested interest to keep the national budget in their favor. Some groups of pensioners have mobilized in protest against the defense reforms and proposed budgets, claiming that the government is steering funds away from their social security.

Finally, in a nation with few natural resources, human capital is everything. But with a shrinking labor force, the competition for young talent will be fierce. The SDF is also feeling the strain. With a tight budget, Japan’s SDF will find it hard to compete with private corporations offering generous packages to attract new recruits. Further complicating matters, the SDF shares a similar recruitment pool with the police and fire services, and as a result, enlisting male high-school graduates is harder than ever.

In a January 2015 public opinion survey, 92.2 percent of Japanese surveyed said that they have a very favorable impression of the SDF. This is especially true after viewing the media coverage of the rescue missions during the 2011 Great East Japan Earthquake. But an overwhelming majority (81 percent) imagines that the SDF’s role is in the realm of disaster relief. Only 42 percent said that the SDF’s role should be in international peacekeeping and even less (25 percent) answered that the SDF should be more proactive in its international peacekeeping missions. The expansion of the SDF’s remit in line with the security bills has caused alarm, as the young could potentially be dispatched overseas to areas of conflict and exposed to physical danger. The risk attached to the role of an SDF officer has now become a hotly contested issue—unthinkable in many countries. A nation of fewer children is more cautious.

This structural constraint of demography has become a blind spot for the Abe administration that not only failed to gauge the extent of opposition to its plans, it also failed to anticipate from where opposition might come. In particular, Abe took for granted the backing of the large elderly population, who are traditionally supporters of his Liberal Democratic Party. To be sure, pushing any further reforms through regardless of Japan’s demographic certainties may backfire. Abe is alienating the elderly, his most important constituency. Moreover, the Abe administration’s ambitious plans for Japan to develop its burden-sharing vis-à-vis the United States could prove difficult to achieve. The United States expects a greater commitment from Japan and Abe has given assurances that Japan can deliver. But domestic pressures may limit Japan’s ability to live up to its expanded defense commitments. Unable to fulfill its duties on the ground, an expectation gap could emerge if Washington fails to appreciate Japan’s limitations, as the University of Indiana scholar Adam Liff has cautioned. Just as Abe is seeking to strengthen the U.S.-Japanese alliance, and by extension to consolidate deterrence in the region, the relationship could inadvertently be strained. The American public could grow tired of spending taxpayer money on a defense budget that goes towards maintaining forward presence far from its borders, and protecting a Japan that does little to reciprocate. Japan may once again be labeled as an international free rider.

A graying Europe faces the same challenge. Burdensome welfare states and continuous cuts to defense spending have left many of the European NATO members with defense budgets that fail to meet the alliance’s 2 percent of GDP benchmark. In dollar terms, the United States alone spends nearly three times that of all its European partners combined. Meanwhile, Russia’s military intervention into Ukraine came as a rude awakening—Europe is still a dangerous place. The debate surrounding international-security burden sharing and free riding is beginning to reemerge. There is a real risk that expectation gaps could develop as a permanent feature of America’s relationships with its allies.

Japan’s demographic problem should also be a concern for the United States. At the dawn of the Cold War era, George Kennan acknowledged the importance of rebuilding Japan and “the restoration of her ability to contribute constructively to the stability and prosperity of the Far Eastern region.” These words are still relevant today. Indeed, the United States must continue to recognize that a strong Japan is vital to the long-term success of its rebalance to Asia and that population will play a critical role in determining Japan’s economic revitalization and regional relations.

Similarly, the United States cannot overlook the fact that the Indo-Pacific is set for an unprecedented rebalancing in populations. Asia is reported to be the region of growth during this century, but it is also the “population bust belt.” Suffering from fertility rates below replacement level and aging populations, both Singapore and South Korea have set aside large budgets to encourage their citizens to procreate, to little avail. Russia’s demographics are even worse. The society is rapidly aging and mortality rates are high. Moscow is anxious of the country’s demographic disaster, especially in light of the potential migration into its vast, resource-rich far east adjacent to China. China will also experience a reversal of fortunes and would do well to learn from Japan’s lost decade of stagnation. Low fertility means that the demographic structure is shifting from a youthful society with an abundance of cheap labor to an aging one. Despite abandoning its one-child policy, China will nonetheless face population decline by the middle of the century with an estimated quarter of its population over sixty-five—not to mention the challenge of several generations where there is a large proportion of unmarried men due to a gender imbalance caused by the one-child policy and a cultural preference for male children.