If the Maine Army National Guard’s 133rd Engineering Battalion is moved to Pennsylvania, the state will lose its oldest and largest military unit, one that has intervened in numerous natural disasters and provided labor and expertise for countless community service projects.

But it’s not clear what Maine would get in return, besides a new infantry unit. A Guard spokesman says engineering units are more difficult to maintain than infantry units, and that the change has been part of the Maine National Guard’s statewide plan since 2008.

That’s just not a good enough answer. For the move to make sense, the National Guard is going to have to make a better argument, and it should be able to make that argument now, if the plan is as far along as it seems. Instead, officials have offered little since the Portland Press Herald broke news of the plan last Wednesday, and what they have said shows the plan offers little to make up for what Maine would be losing.

The 133rd Engineering Battalion has been based in Gardiner, but it was planning to move to Brunswick when its members return from deployment in Afghanistan, where they are helping to dismantle U.S. military bases and combat outposts.

The deployment is the latest for the unit, which has served commendably in Iraq and Afghanistan as well as stateside in what has been a trying 12-plus years for Guardsmen and women. When not building roads, schools and hospitals thousands of miles away, the unit has been back in Maine, lending its efforts and expertise to community projects.

Those projects included work at a Boy Scout camp in Belgrade and a Girl Scout camp in Bridgton, at the Cumberland County and Windsor fairs, and at the Windham school complex and University of Maine-Presque Isle, to name a few.

The 133rd has donated an estimated $110,000 worth of labor to Camp Sunshine, on Sebago Lake, which serves children with life-threatening illnesses, and more than $20,000 worth of labor to Good Will-Hinckley, a school for at-risk youth in central Maine.

The 133rd also has responded to natural disasters, both in Maine and out of state. Members were there for the 2006 flood in York County and the Patriot’s Day storm of 2007, as well as for Hurricane Irene in Vermont in 2011 and “superstorm” Sandy in Connecticut in 2012.

A Maine National Guard spokesman said about 120 engineer-capable soldiers will stay in Maine under the plan. They would form a more agile unit, the spokesman said, one that could better respond to the types of civil emergencies encountered in Maine.

The 133rd’s ability to respond hasn’t been a problem in the past, however, and those soldiers would not be able to conduct community service projects.

There may be reasons at the federal level for moving the Maine battalion. The military is undergoing a shift following the wars in Iraq and Afghanistan, and there are indications that overall changes in the National Guard are having an impact on the makeup of the Maine National Guard.

Supporting that theory are reports that news about the plan caught by surprise Gov. Paul LePage, the commander-in-chief of the Maine National Guard, as well as Maine’s congressional delegation, even though the commander of the Maine National Guard, Brig. Gen. John Campbell, described the move already as “very likely” in an email to the delegation.

If the move in Maine is just one piece of a larger puzzle, Guard officials need to say so, and explain why Maine should lose such a valuable resource for the greater good. Otherwise, there’s no good reason for it, and the 133rd should stay where it is.