According to a hadith from the holy Prophet of Islam (pbuh) those who struggle in the way of God are not allowed to hurt kids and women or poison the water supplies used by the enemy in war.
There is also another hadith about Hadhrat Mahdi (‘a) that he will appear while carrying a sword with him. Here, it is apparent that an old weapon like a sword is not taken in account at the age of Nuclear weapons, but it implies that justice cannot be implemented by modern weapons which bring mass destruction and kill a large number of men whether they are guilty or not.
In addition, we should consider that some soldiers attend the war out of compulsion so that they are always ready to surrender themselves. Therefore, usage of mass destruction weapons is opposed to basic rules of humanity.
As a matter of fact, that kind of victory achieved by modern weapons is not much enduring and cannot last for a long time. In contrast, the positive aspects of victory in classic wars are far greater than temporary achievements by clashes of the modern armies.
During the war, Iran was a victim of terrorism and chemical weapons. In spite of this, the founder of the Islamic Republic showed his great opposition to manufacturing of any kind of Weapons of mass destructions (WMD) or nuclear arsenals even for defensive purposes.
Moreover, there are different strategies to defend a country; it should not be only on the part of military forces. Thinkers, philosophers and politicians also play a role in safeguarding the land and interests of its nation.
Another important point is that countries and politicians do not always adopt a good manner to each other. Hostility is the outcome of power-playing by the ill-wished superpowers and dictatorial regimes across the world. Even if one be committed to the ethical rules, the other may not be so. Therefore, each country needs to defend its sovereignty and dignity against the aggression. Do you think that a country like Israel wont attack Iran if they know we are empty-handed unable to defend our land!