Of course you are right violence is a cycle. Unfortunately this is because of the universal law of probability balance. Simply stated this law says that creation at some point in time is always offset by destruction — stars are born and stars die, peace is offset by war, love is offset by hate and on and on.
Humans have made enormous creative strides in technolog over the last century including the devising of very sophisticated and deadly nuclear weapons.
It is only a matter of time until all this fabulous creation is totally taken out — including all life of earth — by a massive nuclear exchange. This final earthly offset my occur as a of a technical glitch, a political miscalculation or a terrorist intent. Either way the law of probability balance will have its grand offset day.