Tesipiz putting gunpowder into a clay pot. Tesipiz is a Knight of Ahura-Mazda grenadier.
Explosion pots (Juuchwa in Anatropa or Dzesta in Korkin) are clay pots filled with gunpowder and sometimes metal scraps to increase fragmentation when the bombs explodes. The first use of explosives by Jamesianoids were by the Garasyim Korkins around 6,220BX(Before Xerxes).
Bombs are effective at filling the area with sharp clay fragments. While armor (around 10mm to 30mm thick , Jamesianoids are strong enough to wear body armor this heavy and still able to run around) used by most warriors of the Greater Jamesos Realm will protect against the fragments and the padding underneath acts as a spall liner catching any shrapnel if the bombs explodes on the armor. The shrapnel and smoke can deal with horses , light infantry and skirmishers, as well as buildings and fortifications.
The Korkins store there bombs in small warehouses. These warehouses are disguised as houses. This simple disguise worked as Garasyim has very few foreign visitors and anyone who tried leaving the Kingdom with bombs or gunpowder was imprisoned in stone. Not only that only Garasyim Korkins knew the smell of gunpowder.
However the Knights of Ahura-Madza , an elite Jamesian religious order learnt about the potential that these grenades could have. So in 630BX, Ssyakizha an elite knight of Ahura-Mazda infiltrated the city of Garasyim , but instead of trying to smuggle bombs out. She decided to use the magic read ability which reads the memories of people by touching their forehead. Ssyakizha was able to infiltrate Garasyim with the help of the Karutu. After finding out the gunpowder formula she escaped by climbing out of the exhaust cave of the hot springs she dropped out into.
After she escaped, Ssyakizha went back to the Temple of Ahura-Mazda to form their grenadier units. It took a while for the Jamesians to perfect the gunpowder formula, train the new units as well as get the necessary materials for it.
The Jamesians like the Garasyim Korkins were also secretive about their gunpowder formula and so far, no other nation gained the ability to make bombs.