In Gaudium et Spes, we are also taught "Any act of war aimed indiscriminately at the destruction of entire cities  or of extensive areas along with their population is a crime against God and man himself. It merits unequivocal and  unhesitating condemnation"

However, there appear to be many  Catholic who may not concur with these teachings, especially as there appear to be  increased risks of the potential of other nations using them against the US. Could you comment on how we should address these concerns in our development of nuclear weapons

Catholic leadership, both at the level of the Vatican and here in the United States, has taken a firm stand against any use of nuclear weaponry.  This includes the use of such weapons as a deterrent.  This position actually emerges from the classical just war tradition which has dominated Catholic ethical thinking on war and peace issues for centuries.  The argument here is that nuclear weapons would produce such intense and widespread destruction, including the loss of human lives, that would make it impossible to met a key criterion of that just war tradition, i.e., proportionality.  The damage inflicted by the weapons would far surpass whatever good might theoretically result from "winning the war" through the use of such weapons.  And if such weapons are judged as immoral in terms of actual use then we really cannot employ them in a deterrent capacity if in fact we would never be justified in using them.

Let me make it clear, however, that this moral injunction applies only to the use of nuclear weapons, not at the moment to war as such in terms of security and survival.  There have been strong voices for totally eliminating war as a legitimate moral option within parts of the Catholic community, including at the highest levels.  Pope Paul VI's dramatic call for an end to warfare is but one example. Pope John Paul II clearly was moving against the notion of warfare, especially during the Gulf War.  And more recently a meeting at the Vatican on the issue of war and peace co-sponsored by the Vatican's  Justice & Peace Committee and unofficial Catholic peace groups such as Pax Christi  generated a statement against the continued use of any form of war as an instrument of peacemaking. 

That document called for an end to Catholic reliance on the just war tradition as the principal framework for moral decision making.  Instead the Catholic Church should reorient itself towards the promotion of peace in every situation.  Pope Francis himself has shown some sympathy for this perspective.  However, this statement has also received some pushback.  So at this point non-nuclear warfare remains an available moral option from the Catholic perspective especially at the governmental level.  In a recent editorial; The National Catholic Reporter has called upon Pope Francis to make the question of war and peace the focal point of the next episcopal synod.