Clausewitz: how unknown was he?

Harry Smeltzer has found me tangled in the net of a sweeping generalization. I had said, with respect to 1854, Clausewitz was unknown here. He counters:
Do you really think Clausewitz was “unknown” here in the US in 1854? Take a look at note #2 in the first chapter of Halleck’s “Elements of Military Art and Science”, written in 1846. The reader is advised to read “Bynkershock; Vantel; Puffendorf; Clausewitz; and most other writers on international laws and the laws of war.”
Perhaps I should have said, "largely unread" instead of "unknown." Harry adds:
I think people often forget that West Point cadets learned a good deal of French at the academy. The fact that a book had not been translated into English did not mean it was unknown to Americans.
I want to explore this point.

The earliest French edition of any of Clausewitz's writings in book form that I have been able to locate seems to have appeared in 1886. The compilers of the linked bibliography have included periodical references in other parts of the list, so we may tentatively generalize that they found no French serials with Clausewitz content that could have fallen into American hands.

I wonder how many U.S. officers prewar, including Germans, read Clausewitz in German? There are publications of his works in German from the turn of the century onwards; the first edition of On War in German appeared in 1832. It went into a second printing in 1853 which would have made it fairly fresh at the time of the Delafield Commission's visit to Germany. I looked for Clausewitz in the haul of books brought back by the Delafield Commission that was donated to the War Department and have not found him (I am unsure about the completeness of the list I saw). Going through McClellan's writing, published and unpublished, I have not yet found him there either. He gets no mention in correspondence among other figures of the war that I've encountered and he seems to have been absent from Mahan's Napoleon Club at West Point.

There are, however, traces of him in the English literature prewar. From our bibliographic resource:
Clausewitz, Carl von. "On War." Trans./ed. unknown. The Military and Naval Magazine of the United States, v.V and VI (August and September issues, 1835). Originally appeared in The Metropolitan Magazine (London), v.13, May and June 1835, 64-71, 166-176.
Harry's argument is looking pretty good here. There's a little more in a minor vein:
Clausewitz, Carl von. The Campaign of 1812 in Russia. Trans. anonymous [Francis Egerton, Lord Ellesmere]. London: J. Murray, 1843
And here's a bit of a reach:
J.E. Marston, The Life and Campaigns of Field Marshal Prince Blucher (London: Sherwood, Neely, and Jones, 1815). (Marston's book contains what Peter Paret [Clausewitz and the State, p.240, n.46] has described as a "free rendering" of Clausewitz's study of the campaign of 1813 [Der Feldzug von 1813 bis zum Waffenstillstand. Glatz, 1813.])
Clausewitz: seen but not heard. Referred to but little read.

A closing note on Halleck and Clausewitz. Christopher Bassford, in his book Clausewitz in America, says:
Halleck's work on the law of war shows no sign of either Clausewitz's name or influence, despite many areas to which his arguments are relevant. On the other hand, Clausewitz's works are listed three times in the chapter bibliographies in Halleck's 1846 Elements of Military Art and Science, which repeat none of Jomini's negative remarks.
He seems to be a figure to be mentioned only in passing.