Matthew Arnolds "Dover Beach," in all its melancholy bleakness, is one of my favorite poems:The sea is calm to-night.The tide is full, the moon lies fairUpon the straits; on the French coast the lightGleams and is gone; the cliffs of England stand;Glimmering and vast, out in the tranquil bay.Come to the window, sweet is the night-air!Only, from the long line of sprayWhere the sea meets the moon-blanched land,Listen! you hear the grating roarOf pebbles which the waves draw back, and fling,At their return, up the high strand,Begin, and cease, and then again begin,With tremulous cadence slow, and bringThe eternal note of sadness in.Sophocles long agoHeard it on the Aegean, and it broughtInto his mind the turbid ebb and flowOf human misery; weFind also in the sound a thought,Hearing it by this distant northern sea.The Sea of FaithWas once, too, at the full, and round earth's shoreLay like the folds of a bright girdle furled.But now I only hearIts melancholy, long, withdrawing roar,Retreating, to the breathOf the night-wind, down the vast edges drearAnd naked shingles of the world.Ah, love, let us be trueTo one another! for the world, which seemsTo lie before us like a land of dreams,So various, so beautiful, so new,Hath really neither joy, nor love, nor light,Nor certitude, nor peace, nor help for pain;And we are here as on a darkling plainSwept with confused alarms of struggle and flight,Where ignorant armies clash by night.The striking imagery of the last three lines has been the object of a good deal of study. The description by Thucydides of the battle of Epipolae is often cited:

By day certainly the combatants have a clearer notion, though even then by no means of all that takes place, no one knowing much of anything that does not go on in his own immediate neighbourhood; but in a night engagement (and this was the only one that occurred between great armies during the war) how could any one know anything for certain? Although there was a bright moon they saw each other only as men do by moonlight, that is to say, they could distinguish the form of the body, but could not tell for certain whether it was a friend or an enemy.

(Accounts of a night-battle in the Anglo-Sikh War in 1846 have also been proposed as suggesting the image to Arnold.)In his book Theology on Dover Beach, Nicholas Lash wondered if Arnold might have heard John Henry Newman preachthe University Sermon which ends with this paragraph:

To conclude: It will be observed, I have not yet said what Reason really is, or what is its relation to Faith, but have merely contrasted the two together, taking Reason in the sense popularly ascribed to the word. Nor do I aim at more than ascertaining the sense in which the words Faith and Reason are used by Christian and Catholic writers. If I shall succeed in this, I shall be content, without attempting to defend it. Half the controversies in the world are verbal ones; and could they be brought to a plain issue, they would be brought to a prompt termination. Parties engaged in them would then perceive, either that in substance they agreed together, or that their difference was one of first principles. This is the great object to be aimed at in the present age, though confessedly a very arduous one. We need not dispute, we need not prove,we need but define. At all events, let us, if we can, do this first of all; and then see who are left for us to dispute with, what is left for us to prove. Controversy, at least in this age, does not lie between the hosts of heaven, Michael and his Angels on the one side, and the powers of evil on the other; but it is a sort of night battle, where each fights for himself, and friend and foe stand together. When men understand each other's meaning, they see, for the most part, that controversy is either superfluous or hopeless. (Oxford University Sermons, Sermon 10)

The question then might be whether there are sources for Newmans use of the imagery. He would, of course, have been familiar with Thucydides. But he may also have remembered the use of the image of a night battle in two of the Greek Fathers of the Church. In the work in which he defended his flight to avoid being ordained a bishop, St. Gregory Nazianzen has a brutally honest description of the state of the Church at the time, not least of all because of the faults of men in authority. He writes:

Everything has reverted to the original state of things before the world, with its present fair order and form, came into being.... Or, if you will, it is like a battle at night by the faint light of the moon, when none can discern the faces of friends or foes or like a sea fight on the surge, with the driving winds and boiling foam and dashing waves and crashing vessels, with the thrusts of poles, the pipes of boatswains, the groans of the fallen, while we make our voices heard over the din, and not knowing what to do and having, alas! no opportunity for showing our valour, assail one another and fall by one anothers hands.

St. John Chrysostom also used his defense of his flight from ordination as an occasion to reflect on the priesthood, and the same image occurred to him but for a different purpose:

"Nothing clouds the purity of the reason and the perspicuity of mental vision as much as does undisciplined wrath, rushing along with violent impetuosity. "Wrath," someone says, "destroys even the prudent" (Prov 15:1, LXX). For the eye of the soul, when darkened as in some nocturnal battle, is not able to distinguish friends from foes nor the honorable from the unworthy, but handles them all in turn in the same way....

Both of the great saints, of course, were very well schooled and no doubt knew Thucydides backwards and forwards. I wonder if the imagery had become a cultural commonplace.