Just this afternoon, I was reading the chapter in Tenney Frank's Roman Imperialism on the aftermath of the Second Punic War, when Rome found itself in possession of Carthage's Spanish territories and the problems that brought:

...the Spanish tribes were far from ripe for political responsibilities and they had no love for an orderly régime. The negotiations of the sovereign encountered constant difficulties owing to the fact that the people were divided into innumerable tribal groups. No sooner had a Roman general sworn a treaty with a tribe when it reshaped itself Prometheus-like into another form of state and disclaimed participation in the preceding agreement. The policing of Spain degenerated into an undignified and costly guerilla warfare, disgraced by schemes and stratagems. The Roman generals learned to deal in the tricks dealt them. Nowhere did Roman warfare and diplomacy descend to such devious ways as in Spain...Suffice it to say that at various times during the following century the Roman senate would have been relieved to hear that the whole peninsula had disappeared under water.