The Issol A'i (Arithide ['issœl 'a.i]) or Strait of A'i is a narrow strip of water at the eastern edge of the Chisthian Sea separating the continents of Marcasia and Arophania. Measuring approximately 62km in length but only 16km across from Cape Beytes on its north shores to Cape Somorra on its south at its narrowest point, the 330m-deep strait is a rich fishing ground and a vital passage on the main trading routes between Marcasia, Arophania and Istheusia; it was by way of this strait that the Areth first arrived in Calagia from Erdia.
Within 50km of the Issol A'i lie three historically very significant cities: on Cape Somorra, directly overlooking the strait, is Isphea, the ancient imperial capital; some kilometres up the Taphae-Nes river delta lies Lazea, the Areth political, economic and cultural centre; on the opposite bank, little after the point where the strait opens into the Denurean Sea, is the old city of Tannea, fortress capital of the province of Tannaea.
The Issol A'i is also called the Deis Atherris ['ðe.is 'aθəris] in Dethric, or the Kunpaana Sieka [kum'pa:na si.'eka] in Tannaean, both of which mean "Strait of Constriction" in the respective languages. In most other languages of Ilethes, the name of the strait is simply borrowed or derived from the Arithide. The Arithide etymology of the name is uncertain.
The geological history of the Issol A'i is closely tied to that of the Western Boundary Mountain System, along whose route it is sited. As the Maellorian plate pushed up against the Marcasian and Arophanian plates to form the Iryagi and Alerryagi respectively, the crustal level around the location of the strait today rose significantly. The Marcasian and Arophanian plates subsequently accelerated their divergence, and the mountains at the plate boundary sank to form a narrow isthmus connecting the two continents. When sea levels rose due to the Iletheride warming 13 million years ago, the isthmus was submerged to form the Issol A'i, as the now submarine mountains sank further due to waterlogging and the weight of the sea on them, deepening the strait, which eventually reached its present depth of 330m.
Strategic significance & importance
Due to its strategic location at the centre of the three Old World continents, Marcasia, Arophania and Istheusia, and as the only eastern exit from the Chisthian Sea, the Issol A'i has played very significant and important roles throughout history.
Rise of the Areth
The Areth, having very early settled on both shores of the Chisthian, by way of the strait, naturally came to dominate the area. The lack of large expanses of arable land pressured the Areth to turn to the sea, and the rich fishing grounds of the Issol A'i provided them with a natural centre of settlement. Subsequently realising the value of their location astride the major transport routes, the Areth capitalised heavily on it through developing, encouraging and stimulating trade, which was to be the mainstay of their economy for many years to come.
Feudal struggle for control
- Main article: Battles of the Strait
In the years after the fall of the Lazeian Empire, the successor feudal states fought frequently, and occasionally with disastrous results, over the Issol A'i and for control of the lucrative trade routes passing through it. Such battles usually involved tussles over the two most proximate and important cities, Isphea and Lazea, and at the end of the first century after the imperial demise, the two cities had together been besieged 8 times, and attacked 14 times. For a brief period of 38 years, the strait was held by the invading Andu empire from the north, which had overrun the empire's Marcasian holdings in its last days, and captured Isphea and Lazea.
Modern international relations
Situated at a shipping lane bottleneck, the strait has at times served as a very useful tool in international diplomacy.
- In the Zesou Crisis of 1935 CIE, Arithia successfully averted a potentially catastrophic invasion of its ally, Zesou, by closing the strait to ships, military or otherwise, belonging to, registered in or flying the flags of the states party to the Cordial Alliance, which was orchestrating the aggression. The blockade lasted for almost 11 months, during which the Arithide navy sank 29 merchant ships, as well as 5 military vessels of the Alliance in three separate naval battles. The closure was lifted when hostilities ended and a peace treaty was signed, and modern historians estimate the cost of the blockade to the Alliance members to have been between 4 and 7% of GDP.