The series is a re-examination of some of the under-reported and darkest parts of American modern history using little known documents and newly uncovered archival material, looking beyond official versions of events to the deeper causes and implications and exploring how events from the past still have resonant themes for the present day. This episode addresses the historical backround, consequences and reasons behind the use of atomic bombs against the Japanese in the second world war.

Sir David Attenborough reveals the findings of one of the most ambitious scientific studies of our time - an investigation into what is happening to our oceans. He looks at whether it is too late to save their remarkable biodiversity. Attenborough explores some of the ways in which we are affecting marine life - from over-fishing to the acidification of sea water. The film also uncovers the disturbing story of how shipping noise is deafening whales and dolphins, affecting their survival in the future.

Survival of the fittest: Raw competition? Intense cooperation? Both are essential. Interactions between and within species are among the most powerful evolutionary forces on Earth, and understanding them may be a key to our own survival.

Over a person's lifetime they are likely to be prescribed more than 14,000 pills. Antibiotics, cholesterol lowering tablets, anti-depressants, painkillers, even tablets to extend youth and improve performance in bed. These drugs perform minor miracles day after day, but how much is really known about them? Drug discovery often owes as much to serendipity as to science, and that means much is learnt about how medicines work, or even what they do, when they're taken. By investigating some of the most popular pills people pop, Horizon asks, how much can they be trusted to do what they are supposed to?

The fantastical tale of King Arthur, the hero warrior, is one of the great themes of British literature. But was it just invented to restore British pride after the Norman invasion? Michael Wood puts the king in the spotlight.

A look at the story behind Marvel Studios and the Marvel Cinematic Universe, featuring interviews and behind-the-scenes footage from all of the Marvel films, the Marvel One-Shots and "Marvel's Agents of S.H.I.E.L.D.