ive always imagined the arashi's main advantage was living in a place that nobody else coudl live. this leads to a number of advantages: first and foremost beign that every single arashi person is tough as a coffin nail, capable of surviving intense hardship and even bare survival requiring high levels of training and discipline from a young age. an arashi tribe might wander the desert scavenging ships destroyed by sand storms, salvaging the goods meant for foreign markets. because the land they live in is so arid and doesnt support much in the way of food, they are necessarily few in number. because of their harsh conditions, they can hold their own easily, as any who show any kind of weakness do not survive long. generations of such harsh conditions and have created a culture of zero tolerance for weakness, and the commensurate lack thereof. because of this, any regular arashi (as if a 'regular' person could survive in the arashi desert) could be the match of any trained soldier: death and violence are their mothers milk. trained arashi soldiers are near indestructable as the discipline, hardiness, and precision required for survival to adulthood in the desert make them fearsome combatants.
yeshan patrols might wander into the desert to be shot down by an arashi rocket ambushes hidden under sand colored blankets, thrown off in perfect unison. yeshans might then lead an incursion into the desert in force to punish such a brazen attack, and find nothing, the arashi having trained their whole lives for every possible contingency: they have dispersed and hidden in the dunes, nowhere to be found. This sort of ambush tactic coupled with the fact that surviving in the desert for any other nation would require huge supply chains, the sort that could not be protected easily from fast moving small raids by arashi airships and ambushes.
the arashi shouldnt be considered an army, they simply dont have the resources, but small groups of arashi warriors are enough to attack soft targets and blend back into the desert before reinforcements arrive.
not all of the arashi live in scattered bands; some live in cities. Nalm we know from 'Lusse's Travels' was captured by these nomadic people and they inhabit it still. its not hard to imagine that while the baromies, angleans and yeshans are all difficult neighbors to have on your doorstep, as we can see that is the case on the map. nevertheless the arashi have held it 'For generations' indicating that the feirce arashi have flourished there; food now not being such a limitation, as there is an oasis in Nalm, allowing rudimentary, at the very least, agriculture to allow for a denser population. the resiliency and zero tolerance for weakness, now a cultural staple from the desert wandering days would still serve them very well as now that they are in a static position, everyone who has grudges against the arashi now knows where to find them, presumably this would keep the razor sharp edge to the population, as constant war, or the threat of war, weeds out weakness.
thats how i imagine teh arashi anyway, feel free to let me know if you have different ideas, and why! clear skies everyone!