Recommend steps for this paper:
1. lead-in with a historical introduction
2. give an account of the arguments pro and con.
3. state one’s own view
4. give reasons for holding which have universal appeal.
5. consider likely objections or counter-arguments to one’s own position and the reasons  you have given for holding it.
6. respond adequately to these objections or counter-arguments either by trying to argue against them or by revising one’s own position in the light of them.

here are some pro or con that you can put into the essay:
If atrocities do occur, should they be prosecuted by international tribunals?
Nuclear weapons are also prison weapons, so should they be banned?
Guerrilla war falls outside the just war rule, because:
1. the combatants are not in uniform of a nation-state, and the commanders are rebels fighting in civil wars
2. the means they use go beyond what is permitted by the just war doctrine.
3. one cannot easily distinguish between combatants and civilians
4. atrocities do occur.

What justifies war?
1. war should only be fought in self-defense.
2. it should be declared only by the legitimate authority in charge of a nation-state.
3. it should be fought only after a negotiated solution has failed, as a last resort.
4. it should be fought with proportional means which avoid civilian collateral damage.
5. atrocities should not be allowed.
6. pows should be protected under the Genera convention.
7. environment poisoning should be forbidden.