The US military is struggling to keep up with all its responsibilities

Years of complex operations and the ongoing demands of units in the field have left the armed forces struggling to maintain both operational capacity and high levels of readiness, according to a recent report from the Government Accountability Office.

"After more than a decade combatting violent extremists and conducting contingency operations in Afghanistan, Iraq, and most recently Syria, [the Defense Department] has prioritized the rebalancing of its forces in recent budget requests to build and sustain the capabilities necessary to prevail across a full range of potential contingencies," the report states.

"However, DoD has acknowledged that unrelenting demands from geographic commanders for particular types of forces are disrupting manning, training, and equipping cycles," it adds.

Each of the service branches has had some success in addressing readiness issues, but problems remain in some areas for each.

For the Marine Corps, as of February, about 80% of aviation units didn't have the minimum number of aircraft ready for training. The Marines also had a significant shortage of aircraft ready for wartime requirements.

A high pace of operations has also hindered the Navy's maintenance efforts. The service bases its readiness recovery on deployment and maintenance schedules. "However, GAO reported that from 2011 through 2014, only 28 percent of scheduled maintenance was completed on time and just 11 percent for carriers."

Like the Navy, the Air Force has seen continued operations with a shrinking pool of resources and little time for repair and recovery, citing Air Force reports that less than 50% of its forces are at acceptable readiness levels.

The service branch also says it is short of 1,500 pilots and 3,400 aircraft maintainers.

Air Force leaders are looking at several options to address these personnel issues, including heftier retention bonuses and stop-loss policies.

While the Army has seen readiness improvements in recent years, as GAO notes, it continues to have important deficiencies that put it at a disadvantage compared to other countries.

"For example, the Army reports that two thirds of its initial critical formations — units needed at the outset of a major conflict — are at acceptable levels of readiness, but it cautions that it risks consuming readiness as fast as the service can build it given current demands," the report says.

The Army has also gotten withering criticism of its unit readiness from within the service itself.

According to Capt. Scott Metz, who until recently was a

"They will stop for long periods of time in the open with minimal dispersion. They will not effectively use their dismounted infantry and will likely leave them in the back of vehicles for too long, allowing them to be killed with the vehicle. They also will probably make little use of tactical formations and will not use terrain to their advantage."

"makes the case that the Army overtasks subordinates to such a level that it is impossible for Army units and Army leaders to do everything they are tasked to do."

The problem is a deep-rooted one and will take some time to correct, requiring a cultural change starting at the highest levels of the Army's leadership, Metz writes.

Gen. Mark Milley, the Army's chief of staff, told the Senate this month that the Army, like the Air Force, is also suffering from a lack of personnel.

He told the Senate Appropriations' defense subcommittee that the service's portion of US defense strategy, the Army needs an active component of 540,000 to 550,000. That active component is now 476,000.

Though the US armed forces maintains definite advantages over peers and other forces in technology, training, and capabilities, years of operations and, according to many officials, reductions in funding have imperiled the US military's ability overcome opponents and fulfill its missions.