I agree with Andy Hoffman that the Twain/Howells relationship
deserves a full-length re-examination.  I found quite a divergence
between them in their approaches to U.S. imperialism after 1900.
Their different approaches to the Spanish-American War is well
documented in the Twain-Howells correspondence, but after 1900, when
Twain opposed the Philippine-American War, it was assumed that, as
William M. Gibson wrote in his 1947 article on their anti-imperialist
writings, that "their common conviction stimulated their common
effort."  They actually had pretty different convictions (Twain not
being the pacifist Howells was) and took very different approaches to
the issue.   As early as 1902, Howells, who had stuck with the
Republican Party during the Mugwump revolt, supported the
luke-warm anti-imperialism of Jacob Gould Schurman (who wrote the
"blessings of civilization" Philippine plank of the 1900 Republican Party
Platform that Twain blasted in "To the Person Sitting in Darkness"
with his comments on the "Blessings-of-Civilization Trust") and in
1904 and 1905 he joined the anti-imperialist organizations formed in New
York that compromised with the Republican position on Philippine
independence.  Twain's opposition to imperialism did not come
primarily from opposition to war and he stuck with the uncompromising
anti-imperialists after the war in the Philippines was declared over.

Their very different tributes to Carl Schurz, both published in the May
26, 1906, issue of Harper's Weekly, are also very illuminating, I think.
Also, a Howells letter to C. E. Norton (April 6, 1903) in the Indiana
edition of Selected Letters where Howells writes, "I am amused when I
meet Carl Schurz.  We agree entirely, and he comes forward with both
hands out and a glad 'Ah!'  Then we have nothing to say."  I have come
to be very skeptical of statements like this ("we agree entirely") from
Howells, including those he makes in regard to Twain.  His letter to
Norton continues, "The man I have most to say with is Mark
Twain...."  There is also an intriguing letter from Norton to Thomas
Wentworth Higginson (Sept. 2, 1905, T.W. Higginson Papers at
Harvard) where he writes: "Your account of Clemens' simplicity and
unspoiledness is very pleasant, and corresponds with all I have heard
of him from his friends, especially from Howells...."  This was after
the summer Twain and Higginson were neighbors at Dublin, N.H.
That Norton attributes this condescending view of Twain to Howells
is worth looking into, I think.

Jim Zwick