In the mid-1500s, the dominant magical tradition in Europe was that of Catholicism. Priests would use mass prayer as a power source and religious iconography as focusing devices. These were old methods that dated back to before the Roman Empire in various forms and were well ingrained into the tradition of Europe. However, the Protestant Reformation threatened to undermine this tradition.
By removing themselves from the synchronization of Catholic prayer and using different (and fewer) religious icons the spread of Protestantism threatened to break the strength of Catholic religious magic. When England made the switch to Protestantism, the Catholics drew a line in the sand and arranged an intervention. An army was assembled on the continent with the intent to enforce Catholicism on Great Britain. All that was needed was a fleet to escort this army across the English Channel.
An Armada was assembled in Spain for this purpose. It consisted of over 100 ships and was blessed with all of the strength the Catholic Church could muster. They were hoping to take the English fleet by surprise and overwhelm patrol squadrons with superior numbers before the English could organize a defense.
This attempt at surprise was thwarted when druidic shamans in Cornwall were able to spot the Armada’s approach using local divination traditions. According to reports, they were attempting to scry weather patterns to predict future rainfall when they saw a strange anomaly in wind patterns off the coast. Investigating more closely, they were able to identify the presence of a large fleet of ships.
This early warning gave the English time to mount a response. An English fleet was assembled under the command of Sir Francis Drake. Drake, as luck would have it, had studied Roman magical traditions in his time as a sailor. Most of their methods had fallen out of practice in favor of the more religious style in recent years, but Drake had been a part of an effort to revive some of the more practical techniques. This included the use of controlled fog to mask the movement of the English fleet enabling them to take the Spanish by surprise. It also included the localized control of wind and water currents that allowed the English fleet to heavily outmaneuver the Spanish even after they had engaged.
After winning several decisive engagements at sea, the English successfully drove the Spanish Armada into the North Sea. Here, they were set upon by Northumbrian Stormcallers using old Norse techniques that were still in practice by the descendants of Vikings. They didn’t even need to know the exact location of the Armada to affect them. They simply had to ensure that the summer of 1588 was a particularly rough one in the North Sea and North Atlantic. Thanks to their efforts, the already damaged ships attempting to return to Spain via circumnavigating Scotland and Ireland found themselves battered by storm after storm.
In the aftermath of this engagement, the English realized that while a part of their victory was due to the superior craft of their sailors and shipwrights, part of it was also due to their employment of such a wide diversity of magical talents. So, the Royal Navy established a system for educating English spellcasters with great potential. This Royal Society of Wizards soon became a cornerstone of the Admiralty. Within 50 years, the Royal Navy had established a standard practice of having every ship manned by a Society Certified Wizard.
For the next few centuries, English magical supremacy was unmatched. This combined with their practice of embedding Wizards into the Navy led to the English having unparalleled force projection capabilities resulting in the British Empire eventually becoming the largest empire the world had ever seen. Spellcasters around the world learned to respect and fear any spellcasters wearing the uniform of a British officer. Especially ones who had reached the rank of Admiral.
This supremacy was put to the test in the early 1900s with the First World War. While the Prussians could not match English Wizardry at sea, they had pushed their own unique magical tradition by producing some of the world’s best Artificers. This was combined with an effort in turning their industry into high-quality mass production. Suddenly, the British found themselves facing new weapons at sea that they were unprepared for.
England might have ultimately lost the fight at sea if the Royal Navy did not see an influx of a unique kind of volunteer. Warships imbued with significant enough magical energy to become sentient was a phenomenon that was known to the British but something they had so far failed to reproduce or recruit. The German practice of unrestricted submarine warfare was sufficient to convince many of them to fight on the side of the Allied Powers.
This new cohort of recruits included some ships that had previously flown the Jolly Roger and were highly experienced at hunting other vessels at sea. They proved remarkably capable at search and destroy missions against German U-Boats. Against the assembled German High Seas Fleet, they were less effective given their typically smaller size and lighter construction than a modern battleship. However, many sentient ships were able to effectively fill a scouting and escort screening role. On the whole, they proved highly capable of filling the same role as a torpedo-boat destroyer.
After the war, several of the ships returned to civilian status, but many remained. This included ships that were considered family by the unofficial Emperor of the newly formed Romanian Empire. When WWII began, this established elite force of sentient warship was successful in containing the Kriegsmarine to such a significant degree that no equivalent of the High Seas Fleet was able to be formed. The Germans were restricted from open naval confrontations and were restricted to raiding alone.
After the war, Europe settled into a cold war. The tension was split into three distinct factions. There were the Western Democracies, the USSR and its Communist satellite states, and the Romanian Empire and its puppet autocracy buffer states. This left the UK in an odd position.
Nominally, they were a close ally of the United States and France (the leading Democracies). They also had long held to democratic ideals even while maintaining the figurehead of a monarchy. However, there were many who held sympathies for the old style of nobility that the Romanians espoused. In addition, two members of the Royal Family of Romania held commissions in the Royal Navy and were considered war heroes of both World Wars. It was strongly speculated by many who knew the full situation that if the Cold War went hot and NATO was at war with Romania, the UK would dissolve into civil war. No one was confident that the side they backed would win, but everyone knew it would be messy.
This looming potential of a civil war was brought into greater focus when the USSR collapsed. As NATO and Romania scrambled to pick up the pieces, everyone had to hold carefully in their minds that if a war erupted now, it would likely be decided by who won the island of Great Britain. There was no balancing third faction to act as a potential mediator or intervention party.