Recorded with producer Andy Faulkner at Sable Rose Studios in Coventry, England, it was the first Bolt Thrower album since Mercenary (1998) to feature vocalist Karl Willetts, who rejoined the band in November 2004.

Musically, Those Once Loyal incorporates tighter song structures and arrangements into Bolt Thrower's melodic, groove-based sound, while enhancing the production quality of the band's previous albums.

Well received by critics upon release, Those Once Loyal debuted at number 76 on the German Offizielle Top 100 chart, becoming the highest-charting album of Bolt Thrower's career.

[1][2][3] After Ingram left Bolt Thrower in August 2004 to focus on his health,[2][4] guitarist Barry Thomson reconnected with former vocalist Karl Willetts, who agreed to rejoin the band in November 2004.

[18] The album's recording and production were documented in six "studio reports," written by Kearns (with one by Willetts) and posted on Bolt Thrower's official website.

[19][20] During both the writing and recording of Those Once Loyal, Bolt Thrower's songs underwent frequent and meticulous rewrites and revisions concerning their compositions, lyrics, tempos, and the structure of the track listing.

[21]"The Killchain" was written as the final part of a "chain" of six songs, beginning with the title track of Bolt Thrower's debut album In Battle There is No Law!

[38] The opening track of Those Once Loyal, "At First Light", "describes the prelude to going over the top"; Willetts remarked that "waiting and anticipation is a recurring theme throughout the music [Bolt Thrower] create [...] It's about the psychological effects, the feelings.

[15] In a 2014 academic paper discussing the relevance of World War I in popular music, British cultural historian Peter Grant wrote that ...For Victory and Those Once Loyal both "contain highly graphic, though stylised, point-of-view songs, but with no identified protagonist and no sense of the ability of the individual to influence events".

[35][39][40] Bench, who conceived the idea of using the plaque for the cover, stated that Bolt Thrower aimed to distance themselves from the "fantasy battle" artwork used on their previous releases and sought something that was less predictable and more "epic-looking".

[11] In a 2006 interview with Metal Rules, Willetts also stated that the title was intended as a tribute to those who supported Bolt Thrower during their 20-year career, such as John Peel, but "most importantly it’s really aimed at the fans [...] for without them we wouldn’t be here.

[9] Alongside the album's standard CD and vinyl releases, Metal Blade issued a limited edition digipak version of Those Once Loyal, featuring the bonus track "A Symbol of Eight".

[15][54] On 18 January 2006, Bolt Thrower cancelled a planned performance at the Anomalia Club in Prato, Italy, after one of its roadies was electrocuted four times due to reported electrical problems at the venue.

[30] Adrien Begrand of PopMatters praised the band's vocal and instrumental performances on the album, noting how its lyrics describe "the brutality of trench warfare, the empty feeling of facing certain death as the sun rises, and the poignancy of both the quiet battlefield and the granite cenotaphs [...] in remarkably eloquent detail".

[28] As the band's twentieth anniversary approached, several contemporary critics compared the level of innovation in Those Once Loyal with that of Bolt Thrower's previous albums.

In a mixed assessment, James Christopher Monger of AllMusic remarked that Bolt Thrower's lack of change was "either a strength to those who love them or a weakness to their detractors".

[59] Similarly, Adam Chapman of Zero Tolerance stated that the album improved upon the production of their previous albums—although its songs lacked ...For Victory's "instantly memorable riffs".

[62] According to Kez Whelan, writing for The Quietus in 2021, the album displayed Bolt Thrower's "absolute mastery" of their "late-period groove", with every track being "a certified classic".

[36] In 2022, Revolver described the album as "remarkably efficient and still endlessly replayable", emphasizing how it "zeroed in on what [Bolt Thrower had] spent the last 20 years mastering — bulletproof riffs that churn like tanks rolling over stacks of bodies".

Bolt Thrower began writing material for a ninth album in early 2007,[15] and in January 2008, the band announced that they would return to Sable Rose Studios with Faulkner in the summer of 2008.

[74] In a 2017 interview with Metal Hammer, Willetts stated that Bolt Thrower's decision to stop recording albums was "a brave one; we could have carried on and put something out, but in our eyes [Those Once Loyal] was the pinnacle of what we wanted to achieve, [and] we're pleased that we've left a proud legacy behind us.

"[72][N 3] According to Kim Kelly, writing for Vice in 2015, Bolt Thrower's recording hiatus allowed the band to "[bow] out with grace, sending their dead home in a closed coffin instead of propping it up listlessly on life support like so many others of their generation have seen fit to do.