The guns and butter model is used by economists to contrast the costs of spending resources on domestic-economy amenities (butter) or on foreign policy and war (guns). Every government knows, however, that if it plays its cards right, this need not be one or the other. Indeed, the United States with its central banks and its high worker productivity has perfected the art of spending endless amounts of taxpayer money on both guns and butter. Another name for this is the "warfare-welfare state" in which some interest groups (such as low-income voters, agricultural interests, and Social-Security recipients) are bought off with lots of domestic spending, while other interest groups (nationalistic voters and weapons manufacturers and states with lots of military bases) are bought with endless spending on the military.
This is an especially flawless model if you have a central bank like the Fed that can just keep the free money coming with seemingly no end in sight. China has exploiting this model to the fullest in recent years, and now Japan, after years of focusing on free butter, has decided to spend more on the guns. Shinzo Abe, the author of Abenomics (see here for a detailed takedown of Abenomics) has committed his government to numerous rounds of fiscal and monetary stimulus, plus tax increases that funnel plenty of money to his political supporters. Historically, we often find that such enthusiastic government domestic spending is rarely done without plenty of spending on militarization as well. Fascist economic models like those found in Nazi Germany, Mussolini's Italy and Peron's Argentina include plenty of spending both domestically and on war programs.
So, perhaps unsurprisingly, we find that in Japan in recent years, under the leadership of Abe and his party, Japanese nationalism has been on the rise, and now Abe reportedly seeks to reinterpret the Japanese constitution's section on the military, a move that critics claim is designed to pave the way for the Japanese military "to be sent overseas for combat." Abe claims he's just trying to forge closer ties with the US government. This claim, which Abe thinks sounds harmless, should of course set off alarm bells immediately, and suggests that the American state has been pressuring the Japanese government to become a more active adjuct to the US military in east Asia. In any case, it's probably a politically savvy move.
Like so many European and American government before him, he knows he can probably buy acquiescence from antiwar forces with plenty of domestic spending while satisfying the more bellicose inclinations of his friends on the Japanese right wing. With China right next door, military expansion isn't exactly a recipe for avoidance of World War III, but it's not Abe's job to prevent war. It's his job to get his party re-elected.
