The big problem I have with that is Nations usually turn to external conquest and empire-building when things start getting bad at home, as a means of taking the political heat off themselves. Did this not weaken Rome in the long run?
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Your query is both sound and valid, as conquest was a double edged sword for Rome.
In Caesars's time, Europe was essentially Tribal, excepting Greece and Rome.
The most aggressive of these, were the Gauls & Saxons, who crept ever closer to Rome
disrupting trade, a vital source of wealth for the Republic, prompting Caesar's Wars.
Yet there also were Romans who promoted conquest to elevate themselves and fatten
their wallets. Sound familiar?
As time, and Caesar passed, the quality of Roman leadership decayed (as Gibbon noted)
and the result was inevitable.
So, did adventurism weaken Rome over centuries? The truthful answer is yes.