When The Third Punic War ended in 146 B.C. Carthage was eliminated as a rival to Rome, and the Mediterranean Sea became Mare Nostrum. By then Greece was a client state, the Germans were behaving, and except for some problems in Spain the provinces seemed stable. All was not well at home, however, because class problems were about to serve as the spark which would burn down the Republic.
In the paragraphs following I will lay out a chronology showing how the collapse of the Republic became the inevitable outcome of a series of events which undermined the old system and created opportunities for those who wanted power for themselves.