The Ink Factory and Rise Films have partnered with Film4 to develop The American War, a spy drama depicting the fall of Saigon in 1975, which signalled the end of the Vietnam War. Tom Morton-Smith will write the screenplay, which is based on Decent Interval, the bestselling and controversial memoir by CIA operative-turned-whistleblower Frank Snepp, and his autobiography Irreparable Harm.

The film will follow the rising tensions between the intelligence community and a U.S. administration whose refusal to accept the facts prompted a catastrophic compromise of vulnerable American and South Vietnamese personnel and their families, followed by a refugee crisis. Despite this system failure and heart-breaking betrayal, individual acts of heroism and Snepp’s own desperate last-minute efforts to persuade his superiors in Saigon to admit defeat resulted in the evacuation of many people.

Development will be overseen by producers Rhodri Thomas for The Ink Factory, Teddy Leifer for Rise Films and executive Sam Lavender for Film4. Morton-Smith is no stranger to heady American subject matter following his critically acclaimed play Oppenheimer, based on the mastermind behind the creation of the atomic bomb.

“I feel deeply privileged to be partnered wish such innovative filmmakers on a project so close to my heart and so important in illuminating one of the darker moments of a war whose lessons have never been so timely,” said Snepp.

Leifer and Thomas added: “Frank Snepp’s Decent Interval reminds us of the urgent need to speak truth to power. This story resonates now, more than ever, and we are proud to bring it to a wider audience through the hugely talented Tom Morton-Smith.”

London and L.A.-based The Ink Factory is having a banner year. The company produced and financed Jodie Foster starrer Hotel Artemis, which was introduced by Lionsgate to foreign buyers in Berlin. It’s behind hit AMC and BBC drama series The Night Manager, based on John Le Carré’s novel of the same name; Billy Lynn’s Long Halftime Walk, directed by Ang Lee; and Message From The King, an original noir thriller by Stephen Cornwell and Oliver Butcher, which premiered at the Toronto Film Festival last year. The company’s first feature, A Most Wanted Man, based on John le Carré’s novel, was released in 2014.

Rise Films’ credits include The Invisible War, The Interrupters, Knuckle, Dreamcatcher, We Are Together, Rough Aunties and Who Is Dayani Cristal? Starring Gael Garcia Bernal. Film4 is the UK public funding org behind hits such as 12 Years A Slave and Slumdog Millionaire. The company developed Dwayne Johnson’s Fighting With My Family, which was sold to MGM for a whopping $17.5M in Berlin last month.

Morton-Smith is repped by United Agents and Snepp is repped by Intellectual Property Group and Alexander, Lawrence, Frumes & Labowitz.