The entire fleet of H-47 Chinook helicopters have been grounded by the Army in order to fix a part problem in about 70 helicopters.

The U.S. Army has about 400 Chinooks in its fleet around the world, using them to transport troops and equipment as seen in the wars in Afghanistan and Iraq.

Lieutenant General Michael E. Langley was confirmed as the first Black Marine Corps four-star general.

Top Pentagon officials told a House panel that there are now close to 400 reports from military personnel of possible encounters with UFOs.

Officials said in congressional testimony they are "reasonably" sure pyramid-shaped objects in one video were drones.

U.S. Defense Secretary Lloyd Austin said Tuesday that any public statements by world leaders that the conflict in Ukraine could lead to a nuclear confrontation are "unhelpful and dangerous."

Commenting on Pentagon press secretary John Kirby's latest briefing, former U.S. defense official Mick Mulroy says it is unlikely that U.S. troops will be deployed in Ukraine.

ABC News national security and defense analyst Mick Mulroy reacts to the recent Pentagon briefing, talks sending aid to Ukraine.

The Russian warship, “Moskva,” that was badly damaged in combat was one of the ships involved in the now famous run-in with Ukrainian soldiers on Snake Island.

Defense Secretary Lloyd Austin was visually frustrated as GOP Rep. Matt Gaetz attacked his leadership.

ABC News' Stephanie Ramos is live in Ukraine breaking down the troop announcement from the Pentagon and growing tensions between Russia and Ukraine.

Retired Gen. Robert Abrams discusses tactics behind the deployment of more than 3,000 troops to Eastern Europe.

The Department of Defense issued a new report on prohibited extremist activities helping military commanders determine whether service members are actively participating in extremist activities.

The Pentagon has issued a new definition for extremism to identify active participants in prohibited extremist activities.

The Pentagon police officer slain at the Arlington, Virginia, transit center Tuesday was identified as George Gonzalez, an Iraq War veteran.

A Pentagon police officer and his assailant were killed in an incident at the Pentagon Transit Center Tuesday morning, according to two law enforcement sources.

The unpredictable 23-ton rocket is expected to crash into Earth this weekend. Some falling debris is possible. The Defense Department said there are no plans to shoot it down.

The Pentagon police officer who has been charged with murder for allegedly killing two people in Maryland this week, also pulled a gun on a homeless woman last year.

New Pentagon panel to take on sexual assault in the military as Sen. Gillibrand makes impassioned call for changes in how military deals with the issue.

Two female generals who were recently promoted to head four-star combatant commands were spotlighted during remarks in honor of International Women's Day.

Pfc. Asia Graham, 19, was found unresponsive in her barracks on New Year’s Eve.

Army officials are investigating the deaths of Staff Sgt. Jessica Mitchell, 30, and Pvt. Asia Graham, 19, in separate incidents.

They were identified as Sgt. Jessica Mitchell, 30, Pfc. Asia M. Graham, 19.

The Pentagon has informed the CIA that it is weighing an end to most of its support to the CIA's counterterrorism missions.

A three-month investigation into the culture and climate at Fort Hood after the death of Vanessa Guillen found a number of issues, including that the response to sexual harassment was “ineffective.”

The U.S. Army has identified the five soldiers killed in a helicopter crash in Egypt who were serving as peacekeepers in the Sinai Peninsula.

"The Pledge" statue shows a servicewoman bonding with a service dog.

More than a dozen sailors and several civilians have been hospitalized following an explosion on a Navy ship in San Diego on Sunday, officials said.

The Pentagon's latest report on sexual assaults in the military showed a 3% increase in the number of sexual assaults reported last year.

The Pentagon's number three official resigned on Wednesday at the request of President Donald Trump.

The Pentagon could decide in six to eight weeks whether there should be a U.S. military troop reduction in west Africa.

Interest in the draft spiked after a U.S. airstrike killed Iranian Gen. Qassem Soleimani.

The Pentagon expects to send additional U.S. troops to the Middle East after hundreds of protesters attempted to storm the U.S. embassy in Baghdad.

America's top military officer said that U.S. special operations forces captured "two adult males" during the weekend raid that led to the death of the founder and leader of the Islamic State.

An 18-year-old Army recruit at Fort Jackson died on Friday night, after a "medical emergency" that occurred before an outdoor physical training exercise, officials said.

A Fort Hood soldier died from injuries sustained while conducting maintenance on a Bradley Fighting Vehicle.

The agency is cutting almost $400 million from efforts to rebuild military sites in hurricane-ravaged Puerto Rico.

The Pentagon conducted a test of a land-based cruise missile on Sunday, the first such test since the U.S. pulled out of the INF Treaty.

Pentagon issues new guidelines that will open up more press access to senior military and civilian leaders.

The FBI is investigating an Air Force contractor who admitted to printing out and taking home more than 1,000 pages of classified documents marked "top secret."

The Pentagon has released new color images as proof that Iran was behind the attack on tankers in the Gulf of Oman.

National Security Adviser John Bolton said that the U.S. is deploying the USS Abraham Lincoln Carrier Strike Group and a bomber task force to the U.S. Central Command region.

Staff Sgt. Joshua Braica, a Marine Raider, was killed over the weekend in a tactical vehicle accident at Camp Pendleton, California. Two others were injured.

The pilots were conducting a routine training mission.

The Pentagon's top enlisted leader is back on the job after being disciplined administratively after an investigation found he'd violated two ethics rules.

The Pentagon's Office of Inspector General has opened an investigation into complaints of alleged ethics violations against acting Defense Secretary Patrick Shanahan.

The Pentagon quietly released its new policy on transgender service without a statement from the White House, acting Defense Secretary Shanahan or the press office.

The Pentagon's $718 billion budget includes new funding for the border and relies on accounting tricks to get around legal Pentagon funding caps.

The new policy limits the military service of transgender persons currently in uniform to their birth gender, if they are unwilling to do so they could be discharged.

The senator's story is something the military needs to hear.