"Thrice is he armed who knows his quarrel just." The grounds of this conviction may often be tawdry enough, but the conviction is a necessary factor in the case.
The requisite moral sanction may be had on various grounds, and, on the whole, it is not an extremely difficult matter to arrange.

In the simplest and not infrequent case it may turn on a question of equity in respect of trade or investment as between the citizens or subjects of the several rival nations; the Chinese "Open Door" affords as sordid an example as may be desired.

Or it may be only an envious demand for a share in the world's material resources--"A Place in the Sun," as a picturesque phrase describes it; or "The Freedom of the Seas," as another equally vague and equally invidious demand for international equity phrases it.

These demands are put forward with a color of demanding something in the way of equitable opportunity for the commonplace peaceable citizen; but quite plainly they have none but a fanciful bearing on the fortunes of the common man in time of peace, and they have a meaning to the nation only as a fighting unit; apart from their prestige value, these things are worth fighting for only as prospective means of fighting.

The like appeal to the moral sensibilities may, again, be made in the way of a call to self-defense, under the rule of Live and let live; or it may also rest on the more tenuous obligation to safeguard the national integrity of a weaker neighbor, under a broader interpretation of the same equitable rule of Live and let live.