Spying with balloons is not something new

A Chinese balloon seen hovering over Montana this week has been described as an “intelligence-gathering” airship by the Pentagon and a stray civilian research airship by China.

Whatever its intended use, the balloon offers a reminder of how for more than a century, governments have used balloons for surveillance and observation, most often during times of war.

Thomas Paone, curator for the lighter-than-air collection at the National Air and Space Museum in Washington, which includes balloons, blimps and airships, said that while balloon technology has changed over that time, the mission of observation has been a constant.

Here's a look at this history.

Both sides deployed them in the U.S. Civil War.

The Confederate and Union armies used tethered balloons to observe troop movements in what Paone said was the first organized military effort in the United States to use balloons for observation.

The Union had better balloon resources than the Confederates, including a boat to which a balloon was tethered, in what amounted to an early version of an aircraft carrier. One of the Confederates' most-used balloons was eventually captured.

“By mid war, both sides basically give up on balloons because of the logistical challenges that they posed,” Paone said.

Balloon operators in World War I were early adopters of the parachute.

Hydrogen-filled balloons were crucial during World War I to help direct artillery fire, spot troop movements and note enemy positions like depots and trenches.

“As a result, balloons become a prized target of the enemy,” Paone said. Some of the earliest uses of airplanes were missions to destroy them. “When an observation balloon goes up, now everything that you've done or everything you're trying to hide from the enemy can be seen.” And the launch of one was often quickly followed by artillery fire, he added.

Enemy fire could cause a balloon to explode, forcing American balloon observers who saw an attack coming to jump out. They were among the early adopters of parachutes.

Japan sent 9,000 balloons with bombs over the United States in World War II.

The only people to die in an attack on the continental United States during World War II were six people who encountered a Japanese balloon bomb, known as a Fu-Go, during a picnic in Oregon in May 1945.

The victims, Elsie Mitchell and five children from a Sunday school class, were killed when they found the bomb and it exploded.

In Europe, Americans used untethered blimps called K-Ships for observation and in a few cases for attacks.

“K-Ships become a critical aspect of anti-submarine warfare because they can hover and go slow and you can have a whole bunch of people with binoculars looking in all directions at the sea from a pretty good height,” Paone said. “And they're able to see periscopes or other changes in the water that can point to a submarine.”

On D-Day, the 320th Barrage Balloon Battalion, an African American unit, became the first barrage balloon battalion to land in France.

Barrage balloons were large, unmanned tethered balloon whose cables created a hazard for aircraft.