Welsh nationalism is particularly interesting - the first real movement in modern times was the Cymru Fydd home rule movement, started in 1886 by members of the London Welsh - Welsh expatriots, largely middle class, who lived in London. They were inspired by the Irish Home Rule movement, and there’s a lot of overlaps. Cymru Fydd would eventually fizzle out with no real progress, but it did make Wales politically distinct from England. Throughout the early 20th Century this distinction would become more obvious - as England turned Conservative following the Depression, Wales became more Labour, and more Left-Wing which was against the trend. Industrial unrest was often associated with Wales and even had the support of many in the USSR. In 1905 Wales asserted itself in the religious and sporting worlds - defeating the New Zealand rugby team while singing ‘Hen Wlad Fy Nhadau’ despite the official national anthem being ‘God Save the Prince of Wales’ - and the Nonconformist Revival taking place that revolved around Welsh language chapel culture. The 60s is where the Free Wales Army (FWA) come in. Wales had already asserted itself as a seperate entity from England, however politically it was not seperate, it was ruled entirely from Westminster. A series of events led to some Welsh nationalism turning violent - Aberfan, a mining disaster in which 116 schoolchildren were killed at the fault of the NCB - was what inspired John Jenkins to reform Mudiad Amddiffyn Cymru (MAC) - as well as the events surrounding the flooding of the Tryweryn Valley. Jenkins developed a cell structure to MAC (which inspired the IRA’s own structure) and took to bombing pipelines, dams, and other infrastructure, all the while trying to avoid any loss of life. If a bomb failed to detonate an anonymous call to the police would inform them where it was so it could be disposed of. The FWA - headed by Julian Cayo-Evans took credit for many of MACs attacks - and became the popular face of Welsh terrorism partly because of their recognizable symbology, while MAC did most of the wetwork MAC eventually ceased to exist following the attempted bombings surrounding Charles’ investiture as Prince of Wales in Caernarfon. Jenkins was arrested and the campaign mostly ceased. MAC and the FWA, and Meibion Glyndŵr never reached the levels of the IRA for numerous reasons - public support, international support, infrastructure and proximity to England which allowed closer government surveillance. However, the impact they had culturally within Wales was, although not as large as the IRA’s impact along the Irish border - most certainly felt through the Welsh culture of the mid to late 20th century

So, I actually wrote my thesis on some of the Free Welsh Army incidents in reference to the building the Lyn Celyn Reservoir. The reservoir was built to bring water to the city of Liverpool (not in Wales obviously) and in doing so forced a monoglot Welsh village (Capel Celyn) to uproot and relocated its residents. There were a significant protest against this. I have take an excerpt of my dissertation to explain it in reference to the "flooding of Capel Celyn" which is below.

A Powerless United Wales:

A meeting convened by the Liverpool Council was a required precursor to bringing a private bill to Parliament. This meeting was limited to Liverpool tax payers, the residents of Capel Celyn were barred. In spite of this, there was a huge turnout by the Welsh population of Liverpool and the Alderman delayed the start, quickly ferrying in people who looked suspiciously like council employees, some even in Water Board uniforms. The vote was eventually counted with 262 voting in favour of the reservoir and 161 against. It was heard before Parliament on July 3rd 1957. Every Welsh MP opposed the bill (with the exception of one who abstained), but they had little sway with only thirty-six MPs. Even the Minister for Welsh Affairs supported the bill. This was interpreted as the direct support of the reservoir from Downing Street.
On the 1st of August, on its third hearing, the bill was passed. This Act of Parliament overrode any Welsh claim to the land. As Gwynfor Evans said, “the Welsh national community had never been more united, but even a united Wales was powerless”. Once the bill had been ratified by Queen Elizabeth II in August 1957 there was no turning back, eviction notices were issued and the sale of livestock, equipment and surrounding land began. The residents moved on of their own volition, as, with no livelihood or community to support them, there was little point in them staying. The village school had its final day on 28th July 1963, followed two months later by the last service in the chapel. The cemetery was concreted over and the land was stripped back until not a wall, hedge or tree was left of the village that had once thrived.

Water Resistance:

The scheme did not go unopposed. A Defence Committee was formed in 1956 and the members scoured Wales for support against the plans. By September that year, a rally in Bala was attended by over four thousand people although it proved futile. There were also a few militant efforts to expel the construction workers from the valley. In September 1962, two men from Monmouthshire broke onto the site and destroyed an electricity transformer. They were both fined £50 but this was no deterrent, as just two months later the site was broken into a second time and a workshop was damaged. Even with heightened security, the third attack was the most severe; on the 10th February 1963, three men broke into the site and set off an explosion that caused severe damage to the main transformer. The violent attempts to stop the flooding only heightened tensions between Welsh Nationalists and the British government.