On the ninth of September 1513, a force of 30,000 men under James IV of Scotland was drawn up on Flodden Hill, facing 26,000 Englishmen. The battlefield was located ten miles south of the border with Scotland, and the Scots king had chosen an excellent defensive position for his army, which carried the latest weaponry - Swiss pikes, early muskets and cannon. The English King Henry VIII was campaigning in France at the time, leaving the Earl of Surrey to command this rump English force against the invading Scots. On paper, the battle was Scotland's to lose, and had James held his position on Flodden Hill it would likely have been a great Scots victory to rank alongside Robert the Bruce's triumph at Bannockburn two hundred years previously. As it happened, Surrey was able to tempt James away from his position and down onto Flodden Field, a muddy swamp which rendered his modern cannon unusable. Three hours of fierce combat later, and James lay dead on the battlefield, the last king to lose his life in battle on British soil.
While this battle was a decisive blow to Scottish hopes at the time, it was not a conflict with many broader repercussions. The importance of the battle is largely symbolic, as it represents the last major example of Scotland and France working in concert against England as signatories to the so-called "Auld Alliance", an ongoing treaty which had imposed strict limits on the strategic options of English rulers since 1295. The terms of the alliance required that if either party was attacked by England, the other would invade English territory, creating a war on two fronts for the English aggressor. This period had also coincided with a long-running English campaign to construct a continental empire from a platform of territories inherited through various marriages. Decisive victories in battles such as Crécy and Agincourt had given England the early advantage in this “Hundred Years War”, but growing French cohesiveness ultimately overwhelmed the invaders and in 1558 Calais, the last great English overseas possession, was lost under Queen Mary I. Forty years later Mary's sister, Elisabeth lies on her deathbed with no heir, and James VI of Scotland rides to London to unify the island under one ruler: King James I of England and Scotland.
It is during this century, the sixteenth, that England’s grand strategy undertakes a significant volte face, as it moves away from land battles and towards naval superiority. This is a much more suitable strategy for an island nation outnumbered by its French neighbours by a ratio of five Frenchmen to every one Englishman, and well-positioned to exploit the predominant Atlantic trade routes of the time. The unification with Scotland allowed Britain to shrink its land forces and to focus on its navy, with the English Channel providing a policeable barrier which proved impermeable to any would-be invader. In fact unified Britain would come to make a strength out of its relatively tiny land army, since necessity dictated that its generals use cunning and diplomacy rather than brute force to achieve British goals; as a consequence colonial forces would often be made up largely of native troops, minimizing British casualties as well as costs. With a fortified moat securing its home territory, Britain was able to build a global empire upon which the sun never set, and as recently as 1982 it was still able to project its power to the southern tip of South America in the Falklands War. This is part of the reason why September's referendum on whether or not Scotland will remain a part of the United Kingdom is so historic for Great Britain.
History has proven repeatedly that the most fraught relationships are between land neighbours who share a border. While Scotland has an ethnic background of Celtic origin and England is historically Anglo-Saxon, both nations have interwoven over the centuries, which along with recent waves of immigration means that the only real evidence of separation is now historical, cultural and (to a fading extent) linguistic. So it is likely that, at least at first, an independent Scotland would be able to do business with the UK. It is also likely, however, that the characters of the two countries would begin to diverge as differing interests and attributes drive them in subtly different directions. The Scottish National Party (SNP) has intimated at various points that it would pursue a Scandinavian model of government, with an egalitarian ethos allied to generous public services, and in Ireland's happier days it expressed admiration for the Irish miracle. It is the likely adoption of Ireland's business policy which might bring the new nation into conflict with London. Ireland has long sought to undercut the UK's corporate taxes, attracting investment from non-EU businesses to whom the idea of an English-speaking EU member just a short hop from the western continent appeals. Edinburgh is five hours by train from London, which is itself less than three hours from Paris. If Scotland successfully enters Europe and adopts the Euro, the UK could find itself flanked by two Celtic Tigers enthusiastically undercutting its prices. This might create tension, particularly as Edinburgh has the potential to compete with London in financial services in a way that Dublin never could.
In addition to economic considerations, Britain's military would immediately suffer if Scotland ended its participation. Several of the British Army's most decorated regiments are Scottish by ancestry, and the loss of these great names would erase many of the regimental legends - these are the stories that every army tells itself and upon which its identity rests. While Scotland makes up only eight per cent of the UK's population, the relatively high levels of poverty north of the border has resulted in a higher percentage of Scots in the armed forces, and these would need to be replaced. Britain's nuclear deterrent, a submarine-borne missile named Trident, is currently stationed at Clyde Naval Base on Scotland's west coast, a sparsely populated natural harbour the like of which would be hard to find in the rest of the UK. In 1964 the UK Continental Shelf Act led to seismic exploration in the North Sea which has yielded considerable quantities of oil, peaking at six million barrels per day in 1999. Reserves are now considerably depleted by 40 years of extraction, but estimates of the field's remaining life have ranged up to 20 years. These reserves would belong to Scotland, which would come as a severe blow to the UK's energy strategy. While shale gas has been drilled in the North-West of England, the country is too well-populated for extraction on a scale that could provide energy security.
An independent Scotland's first strategic imperative would be to join the European Union. The region does not contain sufficient mineral deposits to support its economy, so a co-operative approach from within Europe would be the best way to attract investment. In order to enter the EU, a strong relationship with Germany would be helpful; it is likely that Alex Salmond’s first official visit as Scottish Prime Minister would be to Berlin. A mutual affinity and similar history would provide a foundation for a close Scottish-Irish friendship, while a warm Franco-Scottish relationship has endured, possibly thanks to an undercurrent of anti-English antipathy. Scotland's Scandinavian pretensions suggest a close relationship with Sweden, Denmark and Norway could succeed, while the birthplace of Adam Smith would be likely to preach an inclusive free-market approach that could appeal to some of the newer entrants to the European project in Eastern Europe. One country that has already made its negative feelings clear is Spain, which suspects that any slack offered to the Scots would be taken up with enthusiasm by Catalan separatists. The other major European player is Italy, although that country is in such a state of political turmoil is it hard to predict what type of regime will emerge from the melee. The United States would be likely to treat Scotland as it treats Ireland, with a nostalgic affection that does not include truly taking it seriously. A Scotland on favourable terms with the rest of Europe might prove something of a needle to the UK, using its influence in the bloc to extract concessions from its larger neighbour, particularly if the UK pursues its current strategy of keeping Europe at arm's length.
Meanwhile, a United Kingdom relieved of Scotland would undoubtedly be weakened. The armed forces would be depleted, while for the first time in 400 years England would have to formulate strategies for how to cope with a land invasion. The UK's "special relationship" with the US, already fading, would become even less pronounced due to the former's increased discomfort with providing support for military engagements. This in its turn might make the UK less assertive in Europe, forcing it to become more willing to toe the party line, and removing a major impediment to increased European integration. London, already responsible for 22% of the UK's GDP, would become even more influential, with the rest of England acting as little more than a backdrop to the capital's greatness. On the positive side, with Scotland removed the topographical difficulties of the country become considerably more manageable. A more compact UK shorn of some of its wildest mountain ranges, national parks and isolated islands would provide a more conducive environment to pursuing a concerted communications policy. Following the example of a country like Estonia, a commitment to fibre optic cable and public wifi services could make the UK an effective hub for the provision of a true internet service economy, finally solving the riddle of how the country will relate to the world in the 21st century.