After being quizzed by Congress for cracking the Blackwater scandal, journalist Jeremy Scahill returns to Afghanistan to look into another suspicious event: the murder of innocent men, children and pregnant women in a small village, after which some men were taken away, cruelly interrogated then freed. The killers are mysterious American soldiers who covered their tracks, and their actions were flatly denied (the official story blamed the Taliban) until overwhelming evidence emerged. But the surviving family members have no idea why this happened, and understandably feel a powerful urge to seek revenge.

Scahill almost accepts this as inevitable until he learns of the Joint Special Operations Command, a top-secret elite force commanded by the president himself. They emerged from the shadows when they killed Osama bin Laden, but most Americans have no idea that they operate with impunity all over the globe, sometimes targeting US citizens. They have thousands on their kill list, and Scahill chases the trail to Yemen and Somalia to learn more.

What he finds is far beyond chilling. It reveals an American government that believes itself above the rule of international law, redefining terms to make things sound legitimate and murdering people who aren't accused of any crime. The worst story Scahill follows is that of Anwar Al Aulaqi, an American targeted by for making radical statements. Then shortly after he's killed by a drone, his 16-year-old son is obliterated in a pointed attack. Memos show that both murders were ordered by President Obama.

Filmmaker Rowley follows Scahill into the firing line, both on the battlefield and in interviews and government briefings. Every detail is carefully backed up with first-hand interviews, while Scahill's low-key narration emphasises the gravity of the situation. It's beautifully shot and edited, with a gorgeous David Harrington score. And as Scahill bravely keeps digging, his tenacity is inspiring. The film clearly shows how these violent attacks are creating more terrorists than they kill. And that America has essentially abandoned its founding principles.

A thorn in the American establishment, Vidal was a shapeshifting character who wrote novels, plays, movies and essays. Related to the Kennedys, he knew everyone in politics, literature and Hollywood, even as he challenged them with boldly accurate observations ("Our form of democracy is bribery on the highest scale"). A close friend to Tennessee Williams, he met his soulmate Howard Auster in the 1950s and created homes that were hangouts for everyone who was anyone.

While keeping the focus on Vidal's shockingly astute observations ("Love is a fan club with only two fans."), the film also traces his life as the last in a long line of authors, politicians and innovators. Educated to be a deep, free thinker, he quickly understood, for example, that war is about a handful of people making a lot of money at the expense of a dead generation. So he took on society's "basic values", which he knew were false notions of what is natural. And he of course became persona non grata.

Filmmaker Wrathall collects a terrific array of archival photos and footage, allowing Vidal himself to tell his story (assisted by his literary executor Parini). The film is littered with pithy quotes, anecdotes about hanging out with very famous figures and accounts of his infamous run-ins with the likes of William Buckley, Norman Mailer and Ronald Reagan. JFK was one of his closest friends, yet Vidal called him one of the most disastrous presidents.

His comments on America after 9/11 are terrifying and shockingly prescient, noting that since then the US has waged war without provocation or respect for any other country, while removing habeas corpus and due process at home through the Patriot Act. "We don't have a republic," he sighs. "There's nothing left." Through his career, Vidal's main topic was the evolution of America from republic to empire, a truth no one wants to hear.

By letting Vidal speak for himself, this film reminds us that his account of US history is striking not because it's based on his opinions, but because it's so lucid and revealing, proving the discrepancy between what America should be and what it actually is ("Tax breaks are socialism only for the rich"). It's a stark picture, but Vidal also knew that the truth will win out. Even if it takes a few generations.

Once church-seasoned black singers started performing in the background in concerts and on records in the 1950s, pop music was changed for good. The white girls who read music perfectly were quickly replaced by women who could improvise harmony, echo the central performer and add passion to any song. And there are a handful of these singers who performed on virtually every major hit in rock history, all while wondering if they have what it takes to have a solo career.

Intriguingly, many of them never wanted to be out front. Despite having more raw talent than most big-name acts she sings with (and winning her own Grammy as well), Fischer prefers the quiet life out of the limelight. The belting voices of Clayton, Vega and Lennear are known throughout the industry, and their voices are probably everywhere in your record collection, but their solo careers never took off. Love is the only one who has achieved her own success. And Hill seems to always be on the verge of breaking out.

Listening to these gifted singers tell their stories is fascinating, especially as their anecdotes are illustrated with fantastic footage performances alongside the likes of David Bowie, Ray Charles, The Rolling Stones and Ike and Tina Turner. The film's most jaw-dropping segment follows them through the process of recording Lynyrd Skynyrd's civil rights-tinged anthem Sweet Home Alabama. And there are also terrific stories from musicians like Wonder, Springsteen, Jagger, Sting and Midler.

Filmmaker Neville assembles this seamlessly, with fluid editing and smart juxtaposition of songs, words and images. By the end of the film, we are in love with these women whose voices we already knew. They're also great characters on-screen, showing that they still have far more talent than most of today's pop stars. As one producer asks, "Why do record companies pay so much to re-tune their artists' vocals today, when these women sing every note to perfection?"

The film centres on an extended interview between Morris and Rumsfeld, discussing the hundreds of thousands of memos he sent while in office. These reveal a deep interest in language, using words to make it clear who the good guys and bad guys are (America used "enhanced interrogation" to question "enemy combatants"). After years working for Nixon, Rumsfeld became Secretary of Defense under Ford, then returned to the job 24 years later when George W Bush took office. So he didn't just oversee the end of the Vietnam War, he also launched the War on Terror.

Rumsfeld is a likeable, intelligent man who knows exactly when to flash a wry smile to underscore a point. Articulate and often very funny, he can easily talk himself around an issue, which of course served him well in his legendary Pentagon briefings in the years following 9/11. His core theme, as echoed in the film's title, is that there are things we know we know, things we don't know we don't know and things we know we don't know. But it's the things we don't know that we know that are hardest to nail down.

Indeed, by skirting key issues, Rumsfeld inadvertently reveals some things about himself that we really wish Morris would have pounced on in his interview. Still, there are punchy moments where Morris challenges him with the facts, forcing him to read his own memo contradicting something he has just said. And the accompanying news footage, stills and newspaper graphics fill in the story with enlightening detail.

All of this is expertly assembled, although Morris seems to know that he's missing that crunch moment that reveals everything about this mercurial figure. So he adds a series of unnecessary digital sequences and accompanies the film with a churning, sometimes overpowering Danny Elfman score. There isn't a dull moment, and it's fascinating to watch someone insist that this clearly fraudulent war was justified. But we wish Morris had gone for the jugular.