Power is enslaving. Those possessed of it invariably place themselves into the service of expanding it further. The crudest way for rulers in which to do this is to grab more territories for themselves to rule. It is also the method which in the short term carries the greatest amount of risk. Outcome of any war is determined by so many factors that it is seldom a foregone conclusion. However we can in general determine what sort of realms will in the long term tend to be more successful at attempts at territorial expansion and also more likely to attempt such expansion for that hinges on only a few factors.
The first determinant is geographic position. A realm surrounded by more powerful neighbours is unlikely to attempt or succeed at expansion. A realm surrounded by weaker neighbours is likely to attempt and succeed at expansion. A landlocked realm has less outlets for potential expansion and is less likely to expand. A realm with a wide access to sea routes has many more outlets for expansionism and is more likely to expand. A realm in a geographically strategic region or a region geographically susceptible to invasion is likely to find itself locked in a constant struggle against invasion itself and is less likely to develop to a point where it can launch mayor expansion of its own. On the contrary a realm in a geographically secure location, such as an island, is likely to be granted longer periods of peace which are a boon to development of every sort including of the potential for expansion.
The second determinant is orientation of the sovereign inwards or outwards. A sovereign who spends his resources internally, on controlling and enslaving the populace within his realm is left with less resources to spend externally. Obviously wealth that is spent on building prisons can not be spend on raising an army. The third factor is the ability of the sovereign to appropriate the resources within his realm for his own use. All other things being equal a sovereign which can appropriate a great portion of the resources within his jurisdiction will obviously in the immediate have an advantage over a sovereign who can succeeded in appropriating only a small portion of resources in his jurisdiction for his own use. The forth factor is the absolute amount of resources within the realm. This means the aggregate of availability of strategically important natural resources, the number of population and most crucially the level of wealth within the sovereign's jurisdiction.
These factors are here broken down as four distinct factors but they interact closely and in a complex manner so that they might be broken down differently as well. But the understanding ultimately lies not in the ability to break them down but in understanding how they are connected to each other and to that of their outcomes which concerns us - the potential for expansion. A good example with which to begin examining these dynamics is Prussia, particularly in its 18th century form. A state historically synonymous with its ability to squeeze the populace for the needs of the state to wage war and with the conception of the state as a mere tool for the carrying out of the foreign policy of the sovereign. Its ruthless harnessing of as much resources as possible to be directed for the use in the arena of foreign policy enabled it, a comparatively small state by area and population, to credibly posture as a mayor power and compete with much larger realms. Needless to say this could only be done by putting a great strain on the populace which had to endure much lower standard of living and far fewer freedoms than would otherwise be the case. For all its military strength the Prussian contribution to invention and culture in non-military areas was, compared to those of other Germans, feeble. Equally so its record in economics was poor. Historically the mayor event that prevented Prussia from falling behind was its acquisition at the conclusion of the Napoleonic Wars of the prosperous Rhineland/Westphalia. Failing this Prussia would have probably fell by the wayside of history, on the account of comparative poverty.
Other states which went the path of all out mobilisation for the purpose of the state invariably fell behind. The most clear cut example, Prussia on stimulants so to say, is North Korea. With the Korean War ending in a truce rather than in a settled peace and the country thus technically remaining in a state of war and with the United States maintaining troops just beyond its fortified border and maintaining a trade embargo against it, North Korea, not altogether unreasonably, went the route of militarism building a huge army and subordinating everything within the state to the needs of this army. With the immediate result being that it found itself in a possession of a powerful military with which it could persist in a confrontation with the United States - a superpower - without the need for much flinching, but with the end result of the strain on its populace this exerted being that today it finds itself poverty-stricken and in a possession of a military that is severely outdated in terms of technical equipment.
Equally instructive example is that of the Ottoman Empire, particularly at its most decadent in 18th and 19th century. The Ottoman Empire was another state that exerted a great deal of pressure on its subjects in order to harnesses as much resources for its own use as possible. Particularly its non-Moslem populace was put under a greater strain than any of the European states subjected their populace to, but without anywhere the results of Prussia to show for it. The reason was two fold. While a substantial amount of resources were squeezed from the populace, in a decentralised and inefficiently structured pre-modern state like the Ottoman Empire the larger part of this wealth did not reach the sovereign and could not be employed by him, but was spent by tax collectors, judges, administrators, feudal lords, jannisaries, timariots and other such castes for their own goals. The second reason was that the parasitism of the state and of the state classes had set back and stagnated economic development, keeping the populace in such a state of poverty that it was impossible to detach it from a mayor portion of its produce without causing starvation and rebellion. While Prussia could consume an enormous 40% of the wealth created within its borders each year without killing off its population, for the Ottoman Empire attempt at doing the same would have been suicidal. Such surpluses beyond the subsistence were simply not there.
Great mobilisation of resources for the purpose of the state or the powers behind the state will actually on balance and in the long term result in lowering of expansionist potential rather than the other way around. This is particularly true if it is combined with inefficient modes of governance that put the populace under a disproportionate amount of strain as compared to the amount of resources detached. This is typical of a pre-modern state where the sovereign lacking a professional bureaucracy to aid him in the grabbing of the resources can take possession of them only indirectly through tax farming and tribute from the vassal landholders which will invariably extract a relatively big amount of resources for to be spent by themselves, straining the populace and retarding growth without a benefit to the sovereign. It is also typical of gangster states and banana republics of the present day where the state is de facto subservient to private interests and where resources are harnessed for their own benefit rather for the benefit of the impersonal state.
It is also true of ideological states for a multitude of practical reasons. First, armed with a powerful idea they find it easier to wield power against their populace and subsequently more easily overcome resistance to their appropriation of resources and are thus more likely to extract so much resources in the short term as to all but kill growth in the long term. Second, they are extremely unlikely to channel most of the resources gathered into instruments of foreign policy and expansion, but are instead eager to channel majority of them inwards into projects of social engineering within their borders. However ultimately even militarism of an impersonal, non-ideological state will prove such a strain on economic growth that it will find itself with less potential for territorial expansion than states in possession of more economically vibrant jurisdictions that can more easily maintain and better equip their militaries.
The maintenance of a more potent military than can be realistically afforded does not lend itself to long term expansionist potential. The overriding factor determining this potential is not the ability to raise and properly equip a large military in the short term but maintaining it in the long term. This means that a would be expansionist power has to be populous and wealthy. However of the two, wealth is actually the much more crucial factor, because it is the capital intensive navy and not the manpower intensive land army that is the truly useful tool for expansionism and empire building.
Empires are built in what we will deem 'wars of distance'. For any realm a war of distance is such a war that, even should it be lost, carries no risk of losing anything but the resources directly invested into the war effort. Such a situation arises when the realm fights an opponent which has no real ability to strike back either because it is much weaker, or because it can not traverse geographic obstacles it would need to in order to do so. On the other hand for a realm a 'war of proximity' is such a conflict in which there is a possibility that should the effort be lost that it will be forced to cede territory of make other concessions. In short it is such a war whose worst possible outcome is not merely status quo ante bellum. Of course any war is from the standpoint of at least one belligerent a war of proximity. The most obscure colonialist expedition can be for the people standing in its path it an existential threat and a matter of life and death. Also miscalculation is not out of the question. A sovereign can conceivably launch a war against an opponent he deems to have no ability to threaten his existing possessions, only to discover in the course of the war that that is not so.
Empires can and usually have emerged from wars of proximity, but an empire which persist in waging such high stakes wars must sooner or later face setbacks and see its power rolled down. For example France in the aftermath of its revolution defeated every other power on the continent to in a tightly contested match emerged as the European hegemon, only to lose its status and be defeated and rolled back after launching one war of proximity, the invasion of Russia, too many. No, the empires are truly realised by expansion that does not put the sources of empire`s power at stake, but merely flexes that power. Thus even should they face setbacks and should a colonial adventure misfire, it is only a matter of time until they recuperate. This is not to say a war of distance has to be a small undertaking, the largest to date, the Second Sino-Japanese War cost the Japanese in their own estimate nearly half a million dead.
It is possible that a war against a neighbour be a war of distance, if the neighbour is sufficiently weak and can count on the backing of no, or of only very weak allies. The Mexican-American war was one such war from the perspective of the United States. Despite Mexico being a neighbouring country it was inconceivable that it could come into position where it would threaten US territory thus it was experienced by the Americans as a colonial war. However in most situations the mere existence of a weak realm next to a powerful one is indication enough of its independence being implicitly or explicitly guaranteed by one power or the other or by a larger system of balance of power, thus usually to wage a war of distance requires great mobility that provides the capacity to attack realms other than its immediate neighbours. It is possible such ability exists in relation to movement over land, for example the First Crusade was a war at a distance of West European kings against the Saracens which did not make use of a navy, likewise the Mongols were able to traverse huge distances over land and strike at distant realms without exposing their centre of power. However usually such feats require the use of a powerful navy. Large enough to transport sufficient number of troops and potent enough to defeat any opposing fleets to secure the troops a safe landing. With such a navy many more possibilities are opened for a realm looking for areas to expand in, without the need to put the home territories from which it draws the most resources from at risk. The greater the range of naval power the more numerous the possibilities.
The preeminent naval power enjoys additional benefits in the diplomatic sphere, having within its ability to blockade all other realms, cutting them off from commerce conducted over the seas and holding all of their overseas possessions hostage. This is particularly true if the naval power is geographically secure from attack over land and can thus credibly threaten to wield its navy in such an aggressive manner without a second though. The more modern and able the navies, the more commerce conducted over the seas, and the greater the advantage in naval power the larger this threat looms and the more benefits the naval power will receive from them in the sphere of imperial diplomacy. At no point in time was this more apparent than today when the fact that all the world commerce essentialy takes place at the mercy of the US Navy has allowed for the situation where the whole globe is under the sway of the US but for Russia, China, India and half a dozen other nations, where the prospect of an anti-US coalition is non-existent and where even the other two independent great powers, Russia and China, are only able to maintain under their influence and guarantee the security of only a few critically important neighbours of theirs.
All the world hegemonies to date, the Dutch, the British and the American, were based on naval power. Netherlands was not a populous country and thus could not raise a powerful land army. Britain never attempted to. Its guiding principle was to never enter a European war without an ally on the continent that would supply most of the troops. Initially Prussia and later on France was the preferred partner. The USA too, for all its chest pounding, is not the preeminent land power. It was content to leave the Red Army do most of the heavy lifting in the Second World War and it found itself halted by the Chinese in a conventional land war in Korea in the 1950s.
This is by no means surprising, the land army is manpower intensive. A potent army can be wielded relatively easily even by a realm that is not wealthy if it has enough men that are able to bear arms and that it dares arm. The factor that determines how many of its populace a it can arm being its political organisation in addition to the number of overall people within its borders. Ancient Sparta, daring not to arm the Helots, could arm only a fraction of its populace, while Revolutionary France - the first truly modern state – could, in theory, conscript every able bodied male. Additionally armies can be raised or enlarged relatively quickly through impressment and drill. This means that every realm of some size and not too backward internal organization has if not a potent enough army then at least the potential raise one relatively quickly. Thus with so many competitors and so much potential for building of a coalition against an overly aggressive land power achieving any sort of land power preeminence is a daunting task.
On the other hand a navy large enough to dominate the seas and to act as the means with which to carve out a true world empire can be forged by a very wealthy realm. Which in turn means that the realms where the climate is the most conductive to economic growth are the realms which will be able to, and which therefore will, carve out giant empires. As we know the climate conductive to economic growth is that of economic liberalism. This does not merely mean low taxation. It means recognition of property rights and lack of restrictions on commercial activities which includes, freedom of movement, low prevalence of arbitrary confiscation, low barriers to international trade, no internal customs etc etc. Realms which are most economically liberal are also much more likely to be liberal in other areas. Meaning that it is the most liberal realms which tend to extreme imperialism and adventurism. This is counter-intuitive at first, but not truly. It is only they who have the means to fund their expansionism. For most of the history China was the region that was the most technologically advanced and that was the wealthiest. However its wealth and technology were not sufficient for it to build an overseas empire. The first to build such empires were realms of Western Europe which emerged as the most advanced in the proximity of the 1500s. And which were in relative terms the most liberal with the sovereign and the ruling classes holding the least amount of power over the populace.
The factors that brought this about, the relative decentralisation and fragmentation of power, are well known. Let us at this point only mention that geographic factors played a role in enabling this relative decentralisation and fragmentation to persist instead of it being overtaken by consolidation or simply falling to conquerors. Western Europe was granted relative security by its geography. To its north there was no threat but for Viking raiding which in any case subsided in the 11th century. To its south it was shielded by the Mediterranean Sea that was only crossed by one invasion, that of the Arabs but whom were soon placed on the defensive and definitely defeated in the Iberian in the middle of the 13th century and even sooner than that in Sicily. To its west was the Atlantic and from there there was no threat. It was only geographically exposed to invasion from its east, from the easternmore parts of Europe. However those parts of Europe were locked in a life and death struggle against invaders from further east and therefore in no position to attempt expansion westwards.
After the raids of the Magyars following their Christianization ceased, incursions from what we now deem Eastern Europe into Western Europe became wholly unheard of, while on the contrary attempts at expansion in opposite direction, such as most iconically the sack of Constantinople in 1204, became more frequent. This at a time when the Eastern Roman Empire was still far more advanced than the Western kingdoms. This means that taken as a unit Western Europe was by its geography and a play of history granted a long period of safety. There were wars among Western Europeans, but they involving people of similar culture were not understood as existential conflicts. Instead conflicts were understood as wars of choice, fought by ruling castes with limited consequences for other classes. Thus Western Europe was spared destruction of wealth stemming from incursions by menacing aliens, but more importantly its rulers lacked an important tool to expand their power; appeals to necessity as a consequence of an existential military threat. There were no Arabs, Seljuks, Crusaders, Mongols, Tartars or the Ottomans the kings of Western Europe could point as an existential threat and thus rally all around themselves all the while demanding obedience and enacting regimentation. Instead whenever they went to war they needed to scrape for funding, usually reciprocating for the funds received by granting certain limited freedoms. Also the security enjoyed made the fractitious political organisation viable. When Kievan Rus` similarly fractured into small principalities in a far less forgiving region, the grasslands of Easter Europe, it was soon swept away under the Mongol tide.
Historically freedoms are not expanded by enlightened rulers as gifts to the populace, but are wrestled from them by discontent subjects. Wether they are given as a concession or arrived at with a revolution freedoms always stem from a situation in which the sovereign has been penned into a corner by the populace. Netherlands, England and the United States of America all arrived at a position where they were internally liberal following a rebellion. The Dutch had fought a prolonged rebellion against Spanish overrule, the English had been hand wrestling with their sovereign for centuries, a match that culminated in the Glorious Revolution and was then carried even further by the Thirteen Colonies in their own revolt against king George the Third.
Such risings however generally require a certain amount of external security. They require for the would be insurrectionists to feel they would be able to rise up against this act of theirs having a detrimental effect on the ability of their homeland to defend itself against an external threat. There must exists a situation where in a sense the insurrectionists feel they can rise up without it making them traitors. Here again is where geography comes into play. Obviously it is far easier for the would be insurrectionists to arrive at such a conclusion in a region that is under a very low threat from the outside. A case in point is the American Revolution which followed the so called French and Indian War that removed the potential threat to the Thirteen Colonies posed by France and made possible the agitation against London that would earlier be unimaginable. It was only after the American British were left with a continent all to themselves that they could contemplate seceding from the the British Empire in order to enjoy greater freedoms. It is also no coincidence that traditionally the weakest of the sovereign`s in all of Europe ruled over England – an island. As islanders Englishmen were protected from foreign powers by geography and thus did not have to take into account who may take internal turmoil and a moment of weakness to their advantage and were thus significantly more likely to stand up to their sovereign.
Thus we can sum up our argument as follows. The tension between the populace and its rulers will favour the populace more in secure regions than in regions that are vulnerable to outside threat. Thus it is the realms that are the most geographically secure that will emerge as the least regimented in the long term. It is such realms with the weakest sovereigns where the populace will come to enjoy the greatest amount of freedoms. It is such areas enjoying the least restrictions on commerce and innovative thought that will emerge as the most prosperous. It is the realms with the most prosperous jurisdictions that will have the means and the energy to hurl themselves into the project of expansionism and imperialism. And finally it is the realms with the means to expand their power trough imperial ventures that will so expand it.