Ifound this on google “the existence of agglomeration economies is central to the explanation of how cities increase in size and population, which places the phenomenon on a larger scale. the concentration of economic activity in cities is one reason for their development and growth.” i hope this you for what your looking for.
Notice that nuetral belgium is located between germnay and france. how do you think belgium and the rest of the world regarded germany's violation of belgiums neutrality ?