The Third Punic War was the inevitable result of treaty that was too restrictive and a long standing feud that couldn't be mitigated.
After defeat in the Second war in 202 B.C, Carthage was prohibited from attacking any friend of Rome and also required to pay reparations to the victor. But, over time, the Roman Senate saw hawk and dove factions emerge during arguments over the future of Carthage. The Punic council, looking at Rome from a position of weakness, saw similar factions argue over the risk of provoking their longtime adversary. Adding to the mix, neighbors of the Carthage began to attack her thinking she would not fight back. But she did and finally, in 149 B.C, the efforts Carthage made to protect herself were seen as violations by the hawks in the Roman Senate and war was declared.