What led to the settlement information of independent states of Celtic peoples on the Balkan Peninsula spread leading to the defeat of the Mongols

Explanation:

What led to the settlement and formation of independent states of Slavic peoples on the Balkan Peninsula by the A.D. 400s and 500s? They merged with Celtic and Germanic tribes. The river and estuary systems served as key trade routes. The mountainous terrain allowed them to resist invading armies.

fertile good for trade etc

an informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.