Although apparently surrounded by rivals and subject to internal dissent, the Holy Roman Empire is not the weakling power it might seem. The Emperor is the overlord - for the most part - of vast tracts of Germany and beyond, but his need to keep dissent and disloyalty under control can be a limitation on his power. Few within the Empire feel loyalty to anything beyond their immediate locality, making effective Imperial government almost the same as Imperial military occupation. Added to this is a rivalry with the Pope over who holds the ultimate authority within the Empire: Emperors have created their own Popes and then been excommunicated by the same men!
If, however, the Emperor succeeds in keeping his provinces in line, his powers for further conquest are formidable indeed. Any new lands he takes only add to his power and can, with careful management, eventually be more loyal to the idea of 'the Empire' than the older Imperial provinces inside Germany.
A drive to the east against Poland can give easy pickings providing care is taken. The Poles can have problems of their own on their eastern frontiers, and judicious pressure from Germany can yield real gains. A move to the southeast is possible, into the Balkans and towards the Black Sea, brushing aside or absorbing the petty kingdoms there. To the south, the rich provinces of the Italian peninsular are a temptation with an additional bonus in controlling Rome and thus influencing the Papacy, although this has the risk of causing religious unrest. To the west, the French are often distracted by their wars with England. The Empire, however, needs to avoid war against more than one opponent at a time. A central position may allow the Emperor to strike out in any direction, but he can also be attacked anywhere along his borders.
Finally, no Emperor should overlook the possibilities for power presented by a Crusade when the Pope calls for one. Who is to say what lands might be available in the wake of such an endeavour?
High Era:
Surrounded by rivals and subject to internal dissent, the Holy Roman Empire sometimes appears weak, a realm held together only by the most fragile of bonds. No one within the Empire really thinks of themselves as Imperial subjects - their loyalties are to the principality, the duchy, the free city, or even the village where they live. The Holy Roman Empire seems an ideal in the minds of men more than a physical reality, and in the hands of a weak leader it is sometimes barely this much. But under a strong Emperor, Imperial power can be awesome. The magnates can be forced to bow to Imperial authority, and once dissent and disloyalty are controlled great things can be achieved. The Empire can be held together by force of will and force of arms, and it can be made greater still by both of these.
Above all other strategic considerations, the Emperor must avoid war against more than one opponent at a time. His central position in Europe may allow attacks in any direction, and the Empire can be strongly defended against counterattacks, but a surrounded man is still surrounded, no matter how great his strength. Imperial power needs to be used against one opponent at a time, and Imperial diplomacy should be aimed at making sure enemies do not act in concert.
A drive to the east against Poland or Hungary can be profitable, although the warlike nature of these peoples should not be underestimated. Beyond is the space to expand almost at will. To the west, the French may be distracted by war with England, a long running rivalry that can be exploited. In the north, the Danes will need careful watching, intent as they are on creating their own empire. To the south, the rich provinces of the Italian peninsular are a temptation, and the long-running dispute with the Pope as to the nature of Papal authority may require an army to occupy Rome, even if this results in a religious backlash.
Finally, no Emperor should overlook the possibilities for power presented by a Crusade. Nothing lasting may yet have been achieved in the Holy Lands by Crusaders, but who is to say what benefits might be available to a cunning ruler in the wake of such an adventure?
Late Era:
Over the last century the Holy Roman Emperors have been remarkable and insignificant in turn. One Emperor managed to get himself excommunicated no fewer than three times, was crowned King of Jerusalem (against the wishes of the Church), "forgot" his promises to go on Crusades, and even made an alliance with the Islamic Egypt! For nineteen years there were two Emperors, both so unimportant that the throne had to be considered empty. But most importantly of all, there has been an end to the Hohenstaufen dynasty and the Hapsburgs are the new Imperial family.
The Hapsburgs' holdings and family connections are what now give strength to the title of Emperor. The family are masters at the art of dynastic marriage: few opportunities to extend Hapsburg lands by treaty and marriage are ever ignored! And the lands they gain are held and rarely allowed to leave family control. The Holy Roman Empire may not have the power that it once possessed, but the Hapsburg Emperor is a powerful man in Europe. His lands, wealth and armies are the envy of other monarchs. Even the disapproval of the French-influenced Papacy has not been enough to cause him problems.
Disloyalty still plagues the Empire as its principalities, duchies and free cities all pursue their own policies, but a strong Emperor can overcome these obstacles. In central Europe there are lands to be secured against regional rebels. As long as the homelands of the Empire are secure, there are opportunities for war and diplomacy on all sides. French, Danish, Polish, Hungarian, and Italian lands can all be taken, provided that the other powers can be neutralised at least for the duration of a successful war. A sensible Emperor should always bear in mind that fighting on two borders at once means that Imperial power is, by definition, split. Imperial power, when it can be used against a single target, is crushing. And as long as Imperial diplomacy can keep enemies from uniting, military power can be used in just this fashion.
Finally, no Emperor should overlook opportunities for lasting alliances with kingdoms beyond his immediate neighbours. A counter-strategy of surrounding rivals by alliances or blood-relatives can be very successful in extending Hapsburg and Imperial influence.
