Official counts over the years, newest figure first. Each chart carries its sources and its limits; the dashed lines are our own arithmetic, marked as analysis.
2026 is counted to 14 October: 91 detainees in 51 operations, already more than any full year from 2005 to 2024 (2025: 100). The record is 2004, the year of the Madrid train bombings: 131.
Limits. Spain's own national security report describes most of those detained as self-radicalised, young and with little or no prior link to terrorist organisations; in 2025 almost 30 percent of those tried at the national court were acquitted. An arrest is not a conviction.
Jihadist detainees in Spain: the straight line through 2021-2025 rises by about 16 a year; carried to 2027 it gives about 132. 2026 to 14 October 2026: 91. At the same pace to 31 December: about 116. This is arithmetic on the published figures, not a forecast by any authority; the dashed segments and figures with a question mark are ours.
After the 2015-2017 peak, arrests fell to 254 in 2020 and have risen in four of the five years since, to 347 in 2025.
Limits. Until 2019 the figures include the United Kingdom; from 2020 they do not, so the drop between 2019 and 2020 is partly the UK leaving the count. Europol warns that the threat cannot be judged from counts alone (TE-SAT 2026, p. 18).
Jihadist arrests: the straight line through 2021-2025 rises by about 20 a year; carried to 2027 it gives about 378. This is arithmetic on the published figures, not a forecast by any authority; the dashed segments and figures with a question mark are ours.
From 6 in 2022 to 14 in 2023 and 24 in each of 2024 and 2025.
Limits. Until 2019 the figures include the United Kingdom. In 2025, 22 attacks of all ideologies were completed and killed 6 people, against 151 dead in 2015 (TE-SAT). Most recent attackers acted alone with simple means.
Jihadist attacks: the straight line through 2021-2025 rises by about 4 a year; carried to 2027 it gives about 33. This is arithmetic on the published figures, not a forecast by any authority; the dashed segments and figures with a question mark are ours.
Suspects rose from 148 in 2023 to 272 in 2025; recorded offences from 152 to 306.
Limits. Austria's state security service changed its classification for 2023, so that year is not fully comparable. Three years are too few for a projection; none is drawn.
Germany's domestic intelligence service estimates the people it attributes to the Islamist spectrum at 28,645 in 2025, up from 27,200 in 2023; it puts 9,110 of them in the violence-oriented part (9,540 in 2024).
Limits. An estimate, not a count of offenders; the level has stayed between about 27,000 and 29,000 since 2019. Earlier editions could not be opened on the service's own site and are not shown.
Islamist Personenpotenzial: the straight line through 2021-2025 rises by about 151 a year; carried to 2027 it gives about 28583. This is arithmetic on the published figures, not a forecast by any authority; the dashed segments and figures with a question mark are ours.
Islamist-extremist prisoners are the largest group (157 in 2026, about where they have been since 2021); the extreme right-wing group has risen from 49 to 80 over the same five years.
Limits. In the year to June 2026 terrorism arrests in Great Britain jumped to 3,867, but 3,630 of them concerned support for Palestine Action, proscribed in July 2025, which the Home Office does not class as Islamist; without them the count was 237 (234 a year earlier).
Islamist-extremist: the line through 2022-2026 is flat; carried to 2028 it gives about 158. Extreme right-wing: the straight line through 2022-2026 rises by about 5 a year; carried to 2028 it gives about 89. This is arithmetic on the published figures, not a forecast by any authority; the dashed segments and figures with a question mark are ours.