The Pentagon may have been instructed not to plan for sequestration, but that guidance may result in an inter-service showdown come next April, should the $1 trillion reduction in government spending take effect.

The director of the White House Office of Management and Budget (OMB) and the deputy defense secretary have explained sequestration as a straight, clean, across-the-board cut. But in the absence of new, clear guidance from OMB, the military services are making their own plans, says Maren Leed, a senior adviser at the Center for Strategic and International Studies and a former aide to Army Chief of Staff Gen. Raymond Odierno.

And those plans are being made at high levels and in a stovepiped way. “They’re thinking about them in their corners and very secretly,” Leed says.

The result is that each service may have different approaches to cuts in their budgets that are likely to have a number of unintended consequences on everything from training and maintenance to military construction. “We’re going to screw this up over and over again,” Leed says.

The real effects of sequestration are not likely to be felt immediately. But as the Pentagon begins planning to implement it at the start of the year, it will be drafting a fiscal 2014 budget at the same time—and that could involve major fights over the pace and scale of reductions to some of the most contentious issues: force structure, the balance between active-duty and reserve forces, and military benefits, in addition to which investment programs might be cut or killed.

“It’s going to be a bloody, bloody year,” she says. “Come springtime, it’s going to get pretty ugly and it’s going to last through the end of the year.”