The University and College Union (UCU), a trade union representing 110,000 staff at UK universities, ran a major series of connected strikes in 2018–22. The action has been characterised as "something of a milestone" for "impending service sector strikes of the 21st century." In 2018, the dispute concerned proposed changes to the Universities Superannuation Scheme (USS), and employers were represented by Universities UK (UUK). In 2019–20, strike action on USS continued, and action on a parallel dispute over pay equality, workload, casualisation, and pay levels (dubbed the "Four Fights") was added. In the latter dispute, employers were represented by the Universities and Colleges Employers Association (UCEA). The first strike began in February 2018. This strike escalated over fourteen strike days between 22 February and 20 March, and took place at sixty-four universities across the UK. This was the longest ever strike in UK higher-education history. The Office for National Statistics found that in 2018, 66% of all working days lost to strike action were accounted for by the education sector, "due mainly to disputes involving employees of universities". An estimated 42,000 staff went on strike with 575,000 teaching hours being lost. By 28 March, over 700 external examiners had also recorded their resignations in a UCU document. The strikes coincided with an exceptional level of snow and ice from the 2018 British Isles cold wave which added further disruption to education. As of 28 March 2018, more than a million students were estimated to have been affected, with 126,000 students signing petitions calling for fee refunds. Students also occupied campus buildings in support of striking staff at more than a dozen universities. The strikes succeeded in preventing the abolition of defined-benefit pensions in the USS scheme. The second round of strikes ran from 25 November to 4 December 2019, and on fourteen days between 20 February and 13 March 2020. Action in 2020 was curtailed by the onset of the Covid-19 pandemic, the economic effects of which in turn worsened the short-term outlook of the USS pension fund. Following an academic year dominated by online teaching, industrial action resumed, with some branches of UCU and two other campus unions—Unison and Unite—achieving a series of mandates for industrial action and striking, particularly 1–3 December 2021, February 14 to 2 March 2022, 21–1 April for others, and a marking and assessment boycott towards the end of the 2021–22 academic year. The National Union of Students ran a "student strike for education" on 2 March. Action resumed in the 2022–23 academic year, with UCU securing a mandate for industrial action at all UK branches and Unison and Unite gaining mandates at some individual branches, with strikes 24–25 and 30 November. During the period covered by this article, strikes also took place on local disputes at individual universities, including student rent strikes in 2020–21 in the context of universities' failure to provide promised in-person teaching during the COVID-19 pandemic; these are covered (incompletely) in the table of all strike action below. (en)