Defense Secretary Chuck Hagel on Friday ordered major changes in the management of America's nuclear arsenal, and billions in additional spending, to fix "systematic problems" in the wake of a series of embarrassing nuclear missteps. 

In announcing the top-to-bottom changes, the secretary also shed light on how deep the problems really were. He described how three Air Force bases had to share a simple -- yet critical -- wrench that is needed for attaching nuclear warheads to missiles. 

Hagel said operators had to express-ship the wrench across the West so that the bases in North Dakota, Wyoming and Montana could use it. 

"They were creative and innovative and they made it work," Hagel said. But he said "that's not the way to do it" and the department now has provided a wrench for each location - and they'll soon have two at each. 

"That's one of many of the issues and the problems that we found," Hagel said. 

Hagel said a lack of sustained attention and investment in the force overall caused it to "slowly back downhill." 

Speaking to Pentagon reporters, he said the Defense Department will boost spending on the nuclear forces by about 10 percent a year for the next five years -- an increase of nearly $10 billion -- adding there is no problem on this issue the Pentagon can't fix. 

"The internal and external reviews I ordered show that a consistent lack of investment and support for our nuclear forces over far too many years has left us with too little margin to cope with mounting stresses," said Hagel, who was flanked by senior Air Force and Navy officers. "The root cause has been a lack of sustained focus, attention, and resources, resulting in a pervasive sense that a career in the nuclear enterprise offers too few opportunities for growth and advancement." 

Hagel ordered two reviews in February -- one by Pentagon officials and a second by outside experts -- as a result of a series of Associated Press stories that revealed lapses in leadership, morale, safety and security at the nation's three nuclear Air Force bases. 

The good news, Hagel said, "is there has been no nuclear exchange in the world." 

Acknowledging the years of neglect, which included glaring problems that prompted then-Defense Secretary Robert Gates to fire his top military and civilian Air Force leaders in 2008, Hagel vowed renewed accountability. 

Navy Adm. Cecil Haney, the head of U.S. Strategic Command, said the nuclear force has been operating securely. 

Hagel's moves are designed to get at the core of the problem. 

The reviews concluded that the structure of U.S. nuclear forces is so incoherent that it cannot be properly managed in its current form, and that this problem explains why top-level officials often are unaware of trouble below them. The reviews found a "disconnect" between what nuclear force leaders say and what they deliver to lower-level troops who execute the missions in the field. 

Among his more significant moves, Hagel authorized the Air Force to put a four-star general in charge of its nuclear forces, according to officials. 

The top Air Force nuclear commander currently is a three-star. Lt. Gen. Stephen Wilson is responsible not only for the 450 Minuteman ICBMs but also the nuclear bomber force. Hagel has concluded that a four-star would be able to exert more influence within the Air Force and send a signal to the entire force that the mission is taken seriously, the defense officials said. 

Hagel also OK'd a proposal to upgrade the top nuclear force official at Air Force headquarters in the Pentagon from a two-star general to a three-star. 

The review's authors, retired Air Force Gen. Larry D. Welch and retired Navy Adm. John C. Harvey Jr., found fault with one of the unique features of life in the nuclear forces. It is called the Personnel Reliability Program, designed to monitor the mental fitness of people to be entrusted with the world's deadliest weapons. 

Over time, that program has devolved into a burdensome administrative exercise that detracts from the mission, the authors found. Hagel ordered an overhaul. 

Hagel concluded that despite tight Pentagon budgets, billions of dollars more will be needed over the next five years to upgrade equipment. That will include a proposal to replace the Vietnam-era UH-1 Huey helicopter fleet that is part of the security forces at ICBM bases. The Air Force declared them out of date years ago but put available resources into other priorities. 

The Navy, which operates nuclear-armed submarines, has had its own problems, including an exam-cheating scandal this year among nuclear reactor training instructors and has suffered from a shortage of personnel. 

When he ordered the reviews, shortly after the Air Force announced it was investigating an exam-cheating ring at one ICBM base and a related drug investigation implicating missile crew members, Hagel was said to be flabbergasted that such misbehavior could be infecting the force. 

Hans Kristensen, a nuclear expert with the Federation of American Scientists, said Thursday that while he had not seen the Hagel reviews or heard what actions Hagel was ordering, he was skeptical that it would make much difference. 

"Throwing money after problems may fix some technical issues but it is unlikely to resolve the dissolution that must come from sitting in a silo hole in the Midwest with missiles on high alert to respond to a nuclear attack that is unlikely to ever come," Kristensen said. 

A cascade of embarrassments befell the Air Force over the past two years, beginning with an AP story in May 2013 revealing one missile officer's lament of "rot" inside the force. Another AP story in November disclosed that an independent assessment for the Air Force found signs of "burnout" and elevated levels of personal misconduct among missile launch crews and missile security forces. 

Fox News' Justin Fishel and The Associated Press contributed to this report.