But the Pentagon, which proposed changes last year for transportation and intelligence units in Chicopee and on Cape Cod, has expressed frustration with Congress’s insistence on blocking some of its plans to reduce what it considers wasteful or unnecessary force structure across the country.

The annual legislation to authorize military spending, signed by President Obama on Wednesday, includes in its $633.8 billion package several provisions championed in recent months by a coalition of Massachusetts officials and industry groups. It requires the Air National Guard to maintain an intelligence unit on Cape Cod that was set to be closed. And the Air Force Reserve will have to re-study its needs for transport aircraft before cutting in half the fleet of 16 cargo jets at Westover Air Reserve Base in Chicopee.

Other provisions designated some $30 million for improvements to other Bay State military facilities at Fort Devens in Middlesex and Worcester counties and the Massachusetts Military Reservation on Cape Cod.

The legislation “marks a major milestone in our efforts to support infrastructure needs, protect critical jobs and valuable assets, and promote significant new investments for Massachusetts military bases,” Lieutenant Governor Tim Murray, who chairs the Massachusetts Military Asset and Security Strategy Task Force, told the Globe.

Over the past two decades, Massachusetts and other New England states have lost a number of major military facilities in downsizings. In Massachusetts, half a dozen relatively small ones remain, only two of which are active-duty. They are zealously protected by local officials and members of Congress.

The bill preserves the 102d Intelligence Wing at Otis Air National Guard Base, a 24-hour data center that supports troops overseas with “real-time” intelligence from satellites and remotely piloted aircraft. The Air Force had proposed doing away with the unit, along with its 141 personnel, contending the mission could be accomplished by units outside of Massachusetts.

But the law now requires the Pentagon to maintain at least 105,700 personnel in the Air National Guard, in effect locking in the current force structure. Supporting documents compiled by the Air Force note that the figure includes keeping the 141 positions at the 102d, along with 10 personnel at Barnes Air National Guard Base, home of the 104th Fighter Wing, which were also slated to be cut.

“We’ve been working on this all year,” said US Representative William Keating, a Quincy Democrat who represents Otis Air National Guard Base and personally intervened with the Air Force chief of staff, General Mark A. Welsh. “It is a front-line operation in terms of its mission. They are doing it cost-effectively. [The Air Force] did not have an adequate replacement to do that right away.”

Colonel Patrick Cobb, commander of the 102d, also welcomed the news.

“We are very happy and feel very fortunate of the support we have had from our elected leaders in keeping our 141 jobs out here at Otis,” he said.

Meanwhile, in Western Massachusetts, officials at Westover Air Reserve Base have been bracing to lose half of their 16 C-5 Galaxy transport planes by October 2015. The Air Force has proposed to relocate the aircraft, operated by the 439th Airlift Wing, to a base in Texas.

“The eight C-5s are still schedule to transfer,” Air Force spokeswoman Ann Stefanek said Friday, but he noted that the new legislation requires the Air Force to conduct a so-called “mobility requirements study” before making associated changes in force structure.

Lieutenant Colonel Jim Bishop, a spokesman for the 439th, said officials are waiting to see how the Air Force will ultimately decide to allocate the planes.

Across the nation, governors and community leaders have pushed back against the Air Force’s plans to streamline both the Air National Guard and Air Force Reserve. A variety of similar proposals in other states were similarly overturned by Congress.

While the efforts to safeguard the Bay State facilities may be good local politics, they have created tension in Washington at a time of growing deficits.