Geopolitics

Etha-
Modern Etha is divided into several main regions. The cultural, economic, and popular core of the country is the region in the center of the northern half of the landmass. It stretches from Tyro in the south to Denk in the north. Strategically, this large region benefited from several boons which enabled it to project its control over the rest of the landmass.
Defensively, the region is surrounded by mountains to the east which would provide a static and stable frontier and protect the region. To the east, the mighty Aroen cuts off the region from Furanke, which prevents the region from western incursions. Finally, to the south and north the core is bordered by the sea. Although there were invasions from outside of this core, such as eastern nomads, Nivagran raiders, and the Ethernian invasion, these were despite the defensive boundaries and were not as common nor destructive as they were elsewhere in the landmass.
The region is full of rivers, connecting cities throughout the region to one another. Additionally, the Aroen, the great salt river, which divides Etha's core from Furanke, allows trade to pass from south to north and to the sea easily. The sea of Ethanga is also conducive to the trade of the region, allowing Tyro to become an arbitrator of wealth throughout the region. However, there are some negatives to the geography of the region. The Ethaine mountains provide a barrier between Tyro and the rest of the Ethaine region on one side and the rest of the core on the other. This feature is at once responsible for the early kingdom's safety from the northern tribes as well as the crippling disunity between the royally administered part of the kingdom and the ducal territories following the Ethain peace.
Ultimately, however, this territory would prove to be the best throughout the landmass. Shortly behind, however, was Furanke. With long rivers and fertile land, Furanke would become a bread basket for Etha. However, it's largely gestirle featureless terrain and the social development of its ancient and medieval inhabitants meant that large scale states were foreign to Furanke until the time that Etha had nearly united its core. Indeed, it was this endemic disunity that would eventually doom the states of Furanke to Ethain domination.
Most else of Etha provides little in the way of arable land and population. The region of Gerune in the east was historically populated by nomadic tribes because the area could not support a settled lifestyle. In the modern day, with modern crops, the region does produce food of a not insubstantial quantity. Yet it serves a larger role historically as a livestock producing region, and even in the modern day some people of the region still live out a nomadic lifestyle. Farther south in Ethanga, the southern strip of the landmass is largely desert. Historically, the region was divided between tribes and cities which relied upon trade with the Asomians. This part of the landmass was never as populous as the north, although its mountainous and desert terrain did mean that occupation and rule was not easy. Strategically, the region makes foreign invasion onto Etha difficult, and the mountains also hold many metal resources ripe for extraction.
Altogether, Etha is well held together with a strong core imposed upon the weaker fringes. It has ample supply of food and metals, as well as a large population. It's territory is flanked largely in defensive terrain, and then further so by sea, making external threats less of an issue.
Asomia-
Asomia is an old state, having its origins thousands of years ago. It's geographic position as a moderately sized, flat island meant that unity on the island came easy. Even as dynasties fell, a new one would find it quite easy to claim control over the island.
However, Asomia was typically more than a single island. By its birthright, Asomia was a naval empire. The Hamil Ainsolof was a popular place for traders and pirates alike. Beyond Asomia, the body of water has played host to a few other powers at different times, as well. Yet throughout the millennia it was always the Asomian empires which dominated the larger part of the sea. There are several reasons for this. One factor is the geography of the home island itself. As said above, the flat terrain of the island helped to keep a strong force in power. Any dissent on the island had nowhere to hide. Yet despite the relative flatness of the island, there are some rivers which flow down from the center of the island. Two of these important rivers come down to a bay near the traditional Asomian seat of power, through which trade could come in and be brought inland. Another factor to Asomian success is the lack of any serious competitors throughout the region.
Asomia's Rivals.
First and foremost in the Asomian sphere are the close lying islands. Blank and the Pride Islands are traditionally within the empire, either directly or as vassals. Neither have historically had the population nor the geography to challenge Asomian dominance. Beyond these lesser islands lies the second greatest island in the Hamil Ainsolof, Ecret. Ecret is smaller than Asomia- perhaps half the area. Yet it lies closer to the mouth of the Great Channel and is better positioned to handle trade from Shaluach and Cazia. Yet, despite these boons due to geography, the island's own layout handicaps its potential. Ecret's mountainous interior, although providing more rainfall than in Asomia, divides the many rich cities nearer to the coastline from one another. Such a reality meant that there was no unified Ecretian polity that could oppose the Asomians, only divided cities which the Asomians could divide and conquer. Time and again, through Asomian collapse and regime change or Ecretian rebellion, the Ecretians stayed disunited and the Asomians came back.
On the fringes of the Hanil Ainsolof lay the true powers with which the Asomian empires compete. These five regions will be broken down in detail.
The first of these to understand is Shaluach. Shaluach is an old region, and a wealthy one. It has good farmlands and has historically been able to support a large population. Rivers run from deep inside the country which allows goods and people to be transported throughout the country. The southern region is also a temperate rainforest, with plenty of trees for ship building. However, the Shalk lands, despite these boons, have typically never provided the impetus for a naval empire. For one, the Shalk states, states because they were often independent and in conflict, were historically focused on affairs on land. The contest to unite the Shalk states was one reason for this, and another was the influence of the pastorialist peoples to the Eastern steppes.
After Shaluach is Cazia. Cazia, historically, was one of the wealthiest countries on the planet. Plentiful mineral wealth on top of a fertile core allowed them to project their will outwards. However, the center of Gala is a large plateau which limits power projection. This hasn't stopped the Cazians from expanding over it to the eastern coast, however. Indeed, Cazian dominion has expanded and contracted throughout the continent many times. Many of these contractions, however, were due to events on the east coast. Rebellions in Murmastol and elsewhere would reject Cazian authority and even in good times were still unreliable. These territories, due to communication and local sentiment, were not amiable to Cazian power projection. This inhibited Cazian attempt at a major presence in the Hamil Ainsolof. Instead, Cazian trade was primarily focused on the western coast of Gala, with caravans delivering trade to the eastern coast. So although Cazian jewelry and other goods were an important part of the trade system within the Hamil Ainsolof, the Cazian state's direct influence in the maritime trade was severely limited.
North of Shaluach lies the land of Atin. Atin is a hilly land, with many rivers and valleys and with a long coastline. Historically, the Atinians have been a consistent and bitter rival to the Asomian. They have harassed Asomian vessels and have competed for influence in the trade hubs of the Great Channel. However, their nuisances stop there for the most part. An assault or two on Ecret aside, there have been no attempts to invade Asomian territories over the centuries, let alone a serious attack on its core. Instead, the divided nature of Atin would make it easier for the Asomians, and the Rutheinians, to play one group against another. The centuries would see such a strategy keep the Atinians below their neighbors and unable to compete as states.
North of Atin, across the Great Channel, lies Rutheinia- Asomia's greatest historical threat. In the pre-modern era the Rutheinians were divided into many different kingdoms. This, of course, meant that they had political concerns among themselves that inhibited external ventures. Although, some of the western kingdoms, particularly Rolinthia, did present active opposition to Asomian goals. Yet, even at their heights, the Rutheinians were typically more concerned with the Great Channel, not the Hamil Ainsolof. This did, of course, have an effect on Asomian interests in the channel, but this did not inhibit Asomian control of the Hamil Ainsolof.
The final historical competitor to Asomian control of the Hamil Ainsolof was southern Etha. The region known to the Ethains as Asomianoda, named after the Asomians ultimately, was host to an array of cities on the coast. They were nexus points for trade from the north to flow down south into the Hamil Ainsolof. By the nature of their terrain, however, they were dependent on the trade that flowed through them. Their erratic placement made unity amongst them difficult, although not impossible. However, each city essentially acted as its own core with no possible economy of scales. Instead of having an active role in maritime trade, most would fall under Asomian influence or, at some point, direct control. With the rise of Etha, however, this would change somewhat. Instead of Asomianoda being the periphery of the Asomian empire, it would become a periphery of the Ethain empire. At this point in history, Asomianoda became a point of power projection for the Ethains, who would challenge and eventually be able to dominate the Hamil Ainsolof- although, perhaps because of such a reality, the Asomians would develop a close relationship with the Ethains during the modern era.