wsieber raises an excellent point when he underscores the hope for peace as an important tenet of Christian doctrine. The Church has wrestled for all its life with the issue of how one best gets there.
Older than the hymns which I quoted is the thinking of Saint Augustine of Hippo in The City of God, Book XIX, and of Saint Thomas Aquinas in the Summa Theologica, Part II, Question 40. These two great Doctors of the Church are often quoted in support of the "Just War Theory."
The theory suggests that the Church must champion peace and support only those wars which (1) have just cause, (2) are declared by proper authority, (3) possess right intention, (4) have a reasonable probability of success and (5) support an end proportional to the means employed. Aquinas said "Those who wage war justly aim at peace, and so they are not opposed to peace."
I suspect that many late-20th Century Christians are embarrassed by the bellicose imagery in hymns. A classic prayer for the newly baptised in the 1662 English Book of Common Prayer asks that he/she/they "manfully ... fight under [Christ's] banner ... and continue Christ's faithful soldier and servant unto ... his/her/their life's end."
The First and Second World Wars brought the horrors of war so vividly to consciousness that many Christian people were inclined to narrow the scope of those just wars which the Church ought condone.
