Next year will likely see the first serious debate in more than a decade on the size of the U.S. defense budget. But before that happens, President Trump has to decide which side he’s on.

On Dec. 3, in a tweet on the need for the major powers to halt a “major and uncontrollable Arms Race,” Trump decried the U.S. military’s current $716 billion budget, which he signed last year, as “crazy.” Two months earlier, he said, under pressure from his budget director, that next year’s budget would drop to $700 billion.

But then, at a meeting this week, Trump and Secretary of Defense James Mattis reportedly settled on a budget for next year of $750 billion—a nearly 5 percent increase over the current year, which itself represented a 10 percent hike from the year before that.

This is an astonishing sum—larger even than the $733 billion that the military services had requested a few months ago. This means that the Trump-Mattis proposal is almost certainly dead in the water and may not have been serious to begin with. A source quoted in Politico referred to the larger sum as a “negotiating tactic.” Since the services’ request usually gets whittled down (it too is put out there as a bargaining position), it’s fair to assume that the final budget will come out at under $733 billion.

Trump will present his budget in February. Then over the next several months, the armed services and appropriations committees, in the House and Senate, will comb through the line items, wrangle deals, restore programs that are vital to some key lawmaker’s district, slash some other programs that aren’t. Will the final amount go as low as the $700 billion that Trump forecast in October? Possibly. It may go lower still.

One reason is that, starting Jan. 3, for the first time in five years, the Democrats will control one house of Congress. And for the first time this century, many of these Democrats will be inclined to cut the budget. They were not so inclined when Barack Obama was president, as their higher priority was to support him as the leader of their party. (And, by the way, contrary to Republican rhetoric, Obama raised defense spending to levels unseen since the height of the Cold War. In fact over his two terms, Obama’s combined defense budgets exceeded those of President George W. Bush by a total of $817 billion.) Nor did Democrats push to cut defense budgets during George W. Bush’s reign, as those years saw the 9/11 attacks, the start of the global war on terror, and the invasions of Afghanistan and Iraq; and while Bush and his defense secretary, Donald Rumsfeld, used this atmosphere to buy more weapons that had nothing to do with those wars, few lawmakers challenged the requests for fear of being tagged “soft on terrorism.”

Now, though, the Democrats will be appraising the budget of a president who not only leads the opposing party but lacks a coherent foreign policy. It’s not clear why Trump even wants a gargantuan defense budget. He wants to be friends with Vladimir Putin and Kim Jong-un; he disses NATO and long-standing security pacts in the Pacific as wastes of money. What wars—against what foes, to defend what allies—is he trying to deter or preparing to fight?

The incoming chairman of the House Armed Services Committee, Rep. Adam Smith, a Democrat from Washington state, has been outspoken on the need to cut defense spending. On one occasion, he said that $600 billion might be an adequate budget, if it was smartly allocated. And a fair number of Republicans might be willing to look at the upcoming defense budget more critically than usual. Owing to Trump’s massive tax cuts, which Congress passed last year, the federal deficit is approaching $1 trillion—a sum that has made the party’s fiscal hawks go wobbly. In last year’s budget, as a share of discretionary spending, the Defense Department soaked up as much money as all the other federal departments combined. It was the only department whose budget went up at all. Just one weapons program in the entire budget was killed. With Trump desiring still more tax cuts and resurgent Democrats demanding more spending on domestic programs to make up for last year’s deep cuts, something will have to give—and the Pentagon will have to give some of it.

Officials have been quoted as saying that the services’ $733 billion budget request is “strategy-driven”—suggesting that it’s the result of careful calculations of what the military really needs. But this is a meaningless phrase. The Navy could always find some mission for another aircraft carrier; the Air Force could find room on some air base for another wing of fighter planes; the Army would welcome another battalion of tanks. If the generals and admirals were told to itemize their needs without regard to budget limits, their needs would be limitless. There is no such thing as a “strategy-driven” budget. Strategy fundamentally involves the application of resources to needs, given a limit on resources.

Even so, a good part of the budget is driven not by strategy but by bureaucratic politics. In almost every year since the mid-1960s, the budgets for the Army, Navy, and Air Force have been divvied up equally—each service getting one-third of the total—plus or minus 1 or 2 percentage points.

What wars—against what foes, to defend what allies—is he trying to deter or preparing to fight?

One of two inferences can be made from this fact. Either the authors of the 1947 National Security Act were geniuses, defining the roles and missions of the three services in a way that would properly allot them equal budgets through the end of the century and beyond—or the Defense Department is a bureaucracy in much the same way that all departments are bureaucracies.

The fact is, in the mid-1960s, the Joint Chiefs of Staff—weary of the interservice bickering that had plagued their ranks for more than a decade—struck a deal: They would refrain from invading each other’s turf and bad-mouthing each other’s programs, as long as they shared the wealth. Secretaries of defense assented to this arrangement in order to keep the peace within the Pentagon.

In Obama’s last year as president, he and his defense secretary, Ash Carter, broke this rule: The Navy got 36 percent and the Air Force got 35 percent of the defense budget, while the Army got only 29 percent. This made sense: The Navy and Air Force were building lots of ships and tanks, and those things cost lots of money; meanwhile, the Army’s big-ticket items, tanks and other armored vehicles, were no longer needed in large number. But some insiders wondered if the interservice tensions of yore might reignite.

In Trump’s first year, Mattis, a retired Marine four-star general, restored the old rule: The Navy and Air Force each got 34 percent of the budget, while the Army got 32 percent. The Navy’s ships and the Air Force’s planes weren’t getting any cheaper, nor were they bought in smaller number. Rather, the Army was handed a pile of extra money that it probably didn’t need. The split will probably be duplicated in the budget the services are preparing now.

Ending the arrangement would be disruptive; the ensuing war among the services would be hard for Mattis, or whoever might succeed him, to settle. But the game is economically and politically unsustainable. In one form or another, fiscal or bureaucratic, war this winter will come.