Japan, and its alliance with the USA, is central to the unfolding politics of the new space race. This essay draws attention to the ways the Japanese state has positioned its geopolitical and geoeconomic interests related to space in the context of the US–Japan alliance. It probes the material and ideational elements that are driving the Japanese state to closer alignment with its formal ally in the military, civilian, and commercial space domains. But while all these realities bode well for alliance collaboration, there are reasons to be cautious. While the Japanese state has proactively aligned its space policy and postures with the USA, it is not forever caught in the US orbit. Given the uncertain fate of US domestic politics that bears on great power competition, Japan is also prudently positioning for how the status of its ally may evolve. This is what complicates straightforward projections about alliance cooperation and balance of power politics in the unfolding international space order.

Observers of East Asia frequently claim that Japanese nationalism is on the rise, and that Tokyo is abandoning its longtime military restraint. To determine whether these trends are indeed occurring, we define and measure Japan's nationalism and military assertiveness; we measure whether they are rising relative to Japan in the past, and relative to seven other countries.

Drawing from social identity theory, we distinguish between “nationalism” and a more benign “patriotism.” We find in Japan (1) strong patriotism that is stable over time, and no evidence of rising nationalism. Furthermore we find that (2) military assertiveness remains generally low, but it has risen in terms of decreased institutional constraints and peacekeeping activities. Our findings have important implications for academic debates about nationalism and Japanese security policy, and for policy debates about a nascent balancing effort against China.