What to do?
The evil of war in its immensity envelops mere individuals and even societies; trying to roll it back looks foolish. But insofar as we are called into fidelity to Christ, we have no choice but to act, foolish or no. What to do? Where to begin? Once you begin to look around, you will find, I think, an embarassment of riches--we simply have no excuse not to be involved in some community Christian or otherwise actively pursuing the end of these wars and their slaughter of the innocents.
One might look over the sites for the Episcopal Peace Fellowship and the Anglican Pacifist Fellowship, the Catholic Peace Fellowship and the Orthodox Peace Fellowship. But also see: the Interfaith Center for Peace, the Institute for Peace and Justice, an excellent site from the American Friends Service Committee (i.e. from the Quakers), the Baptist Peace Fellowship, the ecumenical Churches for Middle East Peace. This site aims to undo trade in arms, while this international site supports "war resisters." There are many others.
On the other hand, we should also look to the parish level; how can the order of praying express our desire for peace? How many parishes are silent about this stuff, even in their intercessions? How would one preach peace and mercy from the BCP or RCL lectionaries?
One might date the numerical decline of TEC and other mainline denominations from the time of the Vietnam War, when resistance in the churches began to split congregations and encourage some on the left and right to leave. Is that sort of decline necessary to the ecclesial pursuit of justice? Or is there some intentional course that might prevent it, say rendering lucid the requirements of Baptism to the faithful? I do not know, but we surely already have to face up to such questions.