continuing the jam-based studio constructions of the group's previous album, 13 (1999), the album expanded on the use of sampled rhythm loops and brooding, heavy electronic sounds. there are also heavy influences from dance music, hip hop, dub, jazz, and african music, an indication of songwriter damon albarn's expanding musical interests.
Recording sessions started in november 2001, taking place in london, morocco and devon, and finished a year later. the album's primary producer was ben hillier with additional production by norman cook (fatboy slim), and william orbit. at the start of the sessions, guitarist graham coxon had been in rehab for alcoholism. after he re-joined, relationships between him and the other members became strained. after initial recording sessions, coxon left, leaving little of his presence on the finished album. this is the only blur album to not feature coxon as a full-time member; he returned to the band for their next album the magic whip (2015).
Think tank is a loose concept album, which albarn has stated is about "love and politics". albarn, a pacifist, had spoken out against the invasion of afghanistan and, after western nations threatened to invade iraq, took part in the widespread protests against the war. anti-war themes are recurrent in the album as well as in associated artwork and promotional videos. after leaking onto the internet in march, think tank was released on 5 may 2003 and entered the uk albums chart at number one, making it blur's fifth consecutive studio album to reach the top spot.
The album was later certified gold. think tank also reached the top 20 in many other countries, including austria, switzerland, germany, norway and japan. it was their highest charting album in the united states, reaching number 56 on the billboard 200. the album produced three singles, which charted at number 5, number 18 and number 22 respectively on the uk singles chart.