How did the lack of new conquests hurt the roman empire?

The lack of the new conquests hurt the Roman empire by "putting an end to a new source of wealth".

The lack of new conquest was one of the reasons for the decline of the Roman empire. Soldiers of the Roman army left their posts in lack of new conquests and hence, leaders of different empires or the tribes advanced their military, which resulted in the defeat of Rome.

to keep us neatruel and not get involved in any wars

he assumed control of treaty negotiations with a hostile power