RP: The burgeoning trade between the Tedeshan and the Eheni has brought chickpeas, papyrus, and other agricultural products to the Tedeshani, as well as sandstone, and whatever else the Eheni have that the Tedeshani don't. However, the journey between Eheni lands and Tedeshan lands takes several days by boat, and unthinkably long by feet. Time is proto-money, after all, so long travels are bad for business. Not to mention that longer journeys require more provisions, which take away from storage room for trade goods. Transporting fewer trade goods is also bad for business.

Logically, to to reduce these flaws, it makes sense to for the Tedeshan to move closer to their trading partners. Additionally, the southern side of the Tedeshan isthmus has been unpopulated for millennia, despite the northern shore of the isthmus being one of the original Tedeshan heartlands. Which is just silly, but the northern and western reaches of Tedeshan lands were more suitable for agriculture and habitation. Now, that those reaches are solidly settled, and trade to the Eheni making the southern Tedeshan lands new commercial hotbeds, the time is ripe for the Tedeshan to settle the south.

Over the centuries, Tedeshan merchants looking for resupply stations closer to the Eheni have set-up shop on these lands, and Tedeshani villagers who wanted easier access to their swanky trade goods followed suit and have settled in fishing villages on the southern shorelines. These small fishing villages were bolstered by a small stream of Tedeshani refugees from the northeast, fleeing the destruction and carnage of Piroeus and other barbarian Exaanos warlords. Eventually even the interior of these lands came to be inhabited, as the steady stream of settlers continued flowing in, albeit to a much lesser density than the coastlines.

Speaking of the Exaanos, new herds of domesticated livestock adopted from them made the steppes of these new lands more livable, providing a reliable source of food to the inland, where the Tedeshan's traditional fishing expertise was useless. Improved farming techniques, most notably the ard plough and canal irrigation, aided also, and allowed the relatively dry land of the southern steppes to grow crops to a tolerable degree of effectiveness.

References: Tedeshan week 3 techs, Tedeshan diplo with the Eheni, Exaanos invasion of northeastern Tedeshan

Map: https://imgur.com/a/14Tgz4C