History Undercover Season 4: Episode Guide & Ratings

Terrorists find chemical and biological weapons a cost-effective alternative to nuclear arms.

The influenza epidemic of 1918 kills 22 million people worldwide.

Fifty black sailors rebel in protest of unsafe working conditions after two ammunition ships blow up in port during World War II.

Friendship between JFK and Richard Nixon becomes intense rivalry.

North African theater of war; El Alamein; Rommel vs. Montgomery.

The Japanese army seeks to develop biological weapons during World War II.

Subs race to rescue men at sea; only 127 of the 2,000 survive.

In the Depression, U.S. executives tried to guide Soviet industry.

Banks from the United States, England and Switzerland helped fund the Nazi regime.

Altitude tests take place in 1950s New Mexico.

The massacre at Nanking, when Japanese troops overcame a Chinese defense and slaughtered 350,000 prisoners and civilians.

The development of Hitler's airborne arsenal, including Luftwaffe's swept-wing and vertical take-off aircraft and stealth bombers.

A former Luftwaffe pilot moves up to become head of the West German Air Force.

New information about secret spy plane missions flown over communist territories during the Cold War.

Operation Thunderclap rained tons of bombs on Dresden, Germany.

A Russian defector damages the KGB.

U.S. soldiers man the SIGSALY system in a London department store.

The Soviets shoot down an American spy plane.

In the 1950s, plans arise to send a giant, manned spaceship to other planets.

A 1989 explosion on the USS Iowa kills 47 crew members.

The secret duck-and-cover plan during the Cold War included underground bunkers which would have protected top officials if the Soviets attacked.

A farmer's son becomes Pope John XXIII and stirs up an ecumenical hornet's nest.

The sudden death of Pope John Paul I gives rise to rumours of a murder plot.

Pope John Paul II does not allow compromise on moral issues.