What is the origin of the phrase "War never changes"

Ulysses S. Grant, 18th US President is quoted many times as saying this.

I have never advocated war except as means of peace, so seek peace, but prepare for war. Because war... War never changes. War is like winter and winter is coming.

Example source

Edit: However, despite the numerous references to this on the Internet, lack of a proper source means it is probably more likely that this is a misattribution and the actual quote was created by one of the writers on Fallout and read by the narrator, Ron Perlman.

War. War never changes. The Romans waged war to gather slaves and wealth. Spain built an empire from its lust for gold and territory. Hitler shaped a battered Germany into an economic superpower. But war never changes.

Source

Early instances of the exact sentence

Two sources in the Google Books database contain the phrase "War never changes" as a standalone sentence. The earlier of those two matches is from "The Day's Work of a Soldier," in The World's Work: Second War Manual: The Conduct of the War (1914):

"The great Napoleon won his victories because the Grand Army could outmarch the enemy. It is the same to-day. War never changes. Only weapons are new. Yet it is not the weapons, but the men who handle them, who win victories."

This quotation is attributed the head waiter in an unnamed restaurant in an unspecified locale in France, speaking during the first few months of what proved to be a long and monstrous First World War. It is evidently the same quotation that site participant P. O. cites in a comment beneath Jack Graveney's answer as appearing in a book published a year later, Practical Warfare: Chapters on Armies and Navies in Action (1915).

And from U.S. Congress, House Foreign Affairs Committee, American Neutrality Policy: Hearings ... on Present Neutrality Law (1939):

As often as not, our effort to promote peace by maintaining neutrality aided the aggressor and contributed to the calamity of the victim. In the topsy-turvy situation surrounding neutrality, however, war remained the same grim reality. War never changes. It only becomes more bloody and brutal.

Early instances of similar but slightly longer expressions

From "Story of War Told in Field Marshal Haig's Reports," in the New York Tribune (March 14, 1920):

In these interviews [with André de Maricourt], Foch [France's Field Marshal] discusses the immutability of strategic principles. But he says guardedly: "War never changes in its essence; it only changes in its means." Again: "No. War hasn't changed since men have existed. But don't you realize that it really demands a great deal of art?"

From Walter Karig, Battle Report: The War in Korea, volume 6 (1960) [combined snippets], we have this longer-winded version of the expression:

But the means of warfare change from conflict to conflict while the meaning of war never changes: at least, not for Americans. The men who fought from Seoul to the Naktong, who held at Masan, drove through Inchon, blasted a path from Chosin to Hungnam, fought for the same national principles that guided us at Saratoga, at Algiers, at Manila Bay and San Juan Hill, Château-Thierry, Normandy, Leyte. It isn't all idealism.

From American Legion magazine, volumes 138–139 (1995) [combined snippets], we have this variant:

One thing about war never changes. Those who fight them always pray it will end. In Korea, the hope for peace often took a cruel turn, as Robert McGinn of Huntington, W.Va., recalls.

And from Journal of International Affairs, volume 51 (1997) [combined snippets]:

The nature of war never changes; "war," after all, "is an act of force to compel our enemy to do our will," as Karl von Clausewitz stated over a century and a half ago in his book On War.

Early instances in which 'war never changes' something else

There are also a number of matches in Google Books, Elephind, and Hathi Trust search results in which "war never changes" appears as part of a longer thought about things that war cannot change. Two of these may be of particular interest. From the "Confederate Veterans' Excursion," in the Alexandria [Virginia] Gazette (July 23, 1895):

The address of the evening was delivered by Major Conrad. During his speech Major Conrad said: "War decides nothing. War never changes a conviction. War never changes any man's honest sentiment. We accept the result of the civil war." The principal topic of conversation during the evening was the proposed erection of a monument to Gen. Winfield S. Hancock, in New Orleans, by the Confederate Veterans of the United States.

In a letter dated August 6, 1898, from Theodore Roosevelt to his sister Corrine, reprinted in Corinne Roosevelt Robinson, My Brother Theodore Roosevelt (1921):

War never changes its hideous phantasms. The heroism of even modern men (and none the less of the women who let them go) is the one thing to glory and hope in. We pack up tonight. My love to all.

From Funk Blentano and Sorell, quoted in The Thalia (May 5, 1905) a judicial decision issued by the Yokosuka Prize Court, reprinted in Sakuye Takahashi, International Law Applied to the Russo-Japanese War with the Decisions of the Japanese Prize Courts (1908):

The people of the hostile state have their property in a belligerent state, because they rely on the law of the latter in the protection of property right in ordinary times. And as war never changes such national law, such state must respect and protect the enemy’s private property also, as long as it continues to give protection to property rights. Otherwise the result will be that the state violates its own law.

And from "What the War Has Not Changed," in the [Sydney, Australia] Direct Action (April 22, 1916):

The press and the rest of our mentors are very careful not to state that there is one thing which war never changes, which peace never prevents, namely, exploitation. This is a word entirely foreign to their vocabulary. Webster, indeed, tells us it is no longer "in use."

Conclusion

Through the years, a number of people have voiced the view the that war in its essence is always the same. The earliest match in the searches I ran for the exact sentence "War never changes" is attributed to a French waiter in 1914, near the beginning of the First World War. Six years later, however, while thinking back on the recently concluded First World War, France's world-famous Field Marshal Foch says something very similar: "War never changes in its essence."

I suppose that Foch's comments may have had a bit more impact than the waiter's. But I like to imagine that he got the idea one day at a café while eating breakfast and listening to the grumblings of a particularly exasperated server.

On the other hand, Foch's connection to the saying "War never changes" doesn't seem especially well established in the public mind. Wikiquote, for example, lists four quotations from Foch on the subject of war, but Wikiquote attributes the quotation "War never changes" to Scott Campbell, Brian Freyermuth, and Mark O'Green, Fallout, interpreted by Ron Perlman as the narrator (1997).

Similar statements about the immutability of war appear in a Congressional discussion during the uneasy days just prior to the Second World War, shortly after the Korean War, long after the Korean War, and in what appears to be a general retrospective on war written in 1997—the same year that the quotation appeared in Fallout.

Ultimately the most accurate conclusion may be that a lot of people over the years have said "War never changes," and that none of them had to rely on any authority beyond their own experience in reaching that formulation. With the mass-market reach of Fallout, of course, the calculus has changed—because Fallout, unlike Field Marshal Foch, seems to have cultural staying power in today's English-speaking world (and beyond).