A string of live performances and touring with the Backstreet Boys in 2014 sparked interest within the group to reform and record Red Flag.

[4] A limited release of the group's third compilation album, Pure Shores: The Very Best of All Saints, was commissioned by Music Club Deluxe in September 2010.

[7] Unexpectedly the following year, All Saints were invited to perform as special guests for five dates of the Backstreet Boys' In a World Like This Tour in Ireland and the UK.

[4][10] A promotional video was shared by All Saints on social media in June 2015, suggesting an upcoming project and tour.

[10] Similarly, on 1 January 2016, the group posted a promotional image of themselves looking upwards in front of a grey background with the text "2016".

[14] Prior to its development, Lewis had taken notice of a new producer, Hutch, whose work she loved and saw the album as the ideal opportunity for a collaboration with him.

It details Nicole's emotions when it was revealed to her that Gallagher had an affair and was expecting a child with American journalist Liza Ghorbani.

[4][16] Blatt cited Red Flag as the group's best output[14] and her favourite All Saints album and the one she "always wanted [them] to make",[4] while Lewis said it "couldn't feel any more right".

[20] To promote Red Flag, All Saints appeared on Alan Carr: Chatty Man for an interview and a performance of "One Strike" on 17 March 2016.

[23] The show was a critical and commercial success; it received praise from reviewers for The Daily Telegraph and The Guardian, and tickets sold out in one minute.

[12] The Red Flag Tour visited 10 British cities throughout October 2016, beginning in Newcastle upon Tyne and ending in Norwich.

Leonie Cooper of the NME noted a large drop in quality after the track "Summer Rain", ultimately calling Red Flag equally thrilling and disappointing.

[44] While impressed by "One Strike" and "One Woman Man", Harriet Gibsone of The Guardian said the album was beset by "rogue energies" and "mellow ballads of varying degrees of schmaltz".

[42] In his review for The Times, Will Hodgkinson wrote that Red Flag had "some awful filler", but appreciated its genuine musicianship and called it "a far from disgraceful return".

[48] Richard Folland of PopMatters found the second half weaker, dismissing its R&B-influenced style as anonymity, but complimented the album's maturity and variety.

He concluded that the group's complementary harmonies "can conjure an esoteric kind of pop magic" and that they "can still create a sound which few if any of their peers can match.

[50] Red Flag debuted at number three on the UK Albums Chart with first-week sales of 9,298 units, behind The Lumineers' Cleopatra and Adele's 25.