In the midst of all this anti- and pro-war talk, I thought I'd post this, which strikes me as one of Longfellow's best.

The Arsenal at Springfield

THIS is the Arsenal. From floor to ceiling,
Like a huge organ, rise the burnished arms;
But from their silent pipes no anthem pealing
Startles the villages with strange alarms.

Ah! what a sound will rise, how wild and dreary, 5
When the death-angel touches those swift keys!
What loud lament and dismal Miserere
Will mingle with their awful symphonies!

I hear even now the infinite fierce chorus,
The cries of agony, the endless groan, 10
Which, through the ages that have gone before us,
In long reverberations reach our own.

On helm and harness rings the Saxon hammer,
Through Cimbric forest roars the Norseman's song,
And loud, amid the universal clamor, 15
O'er distant deserts sounds the Tartar gong.

I hear the Florentine, who from his palace
Wheels out his battle-bell with dreadful din,
And Aztec priests upon their teocallis
Beat the wild war-drums made of serpent's skin; 20

The tumult of each sacked and burning village;
The shouts that every prayer for mercy drowns;
The soldiers' revels in the midst of pillage;
The wail of famine in beleaguered towns;

The bursting shell, the gateway wrenched asunder, 25
The rattling musketry, the clashing blade;
And ever and anon, in tones of thunder
The diapason of the cannonade.

Is it, O man, with such discordant noises,
With such accursed instruments as these, 30
Thou drownest Nature's sweet and kindly voices,
And jarrest the celestial harmonies?

Were half the power, that fills the world with terror,
Were half the wealth bestowed on camps and courts,
Given to redeem the human mind from error, 35
There were no need of arsenals or forts:

The warrior's name would be a name abhorrèd!
And every nation, that should lift again
Its hand against a brother, on its forehead
Would wear forevermore the curse of Cain! 40

Down the dark future, through long generations,
The echoing sounds grow fainter and then cease;
And like a bell, with solemn, sweet vibrations,
I hear once more the voice of Christ say, "Peace!"

Peace! and no longer from its brazen portals 45
The blast of War's great organ shakes the skies!
But beautiful as songs of the immortals,
The holy melodies of love arise.

Like so much of Longfellow, this one takes a surprising figure -- the arsenal as a musical instrument -- and makes it seem altogether right. I think it is also typical in that its very fluidity probably works against its being much appreciated these days as a work of art. It doesn't bear the marks of its own creation.
By the way, all those images from ages past remind me a little of another once popular and now utterly forgotten poet, Edwin Markham. He never approached Longfellow's standing, but for some years he was probably one of the ten most popular living American poets. His "The Man with the Hoe" still works, and he has some other solid poems.
RPW

The late Judson Jerome, who wrote the poetry column for Writer's Digest for many years, was a big fan of Markham, especially "The Man with the Hoe," which was one of the most famous poems of its era. Dana Gioia has written about it too.

I'm glad you started this line. I have argued in this space before that Longfellow's "Saga of King Olaf" is a neglected masterpiece. While you can always find some textbook that contains bits of "Hiawatha" or "Evangeline", the superior merits of King Olaf wait to be discovered. The poem contains 21 different metrical forms & tells a rousing good story to boot. Here's one my favorite bits.

#20 EINAR TAMBERSKELVER

It was Einer Tamberskelver
Stood beside the mast:
From his yew-bow, tipped with silver,
Flew the arrows fast;
Aimed at Eric unavailing
As he sat concealed,
Half behind the quarter-railing,
Half behind his shield.

First an arrow struck the tiller
Just above his head;
"Sing, O Eyvind Skaldaspiller,"
Then Earl Eric said.
"Sing the song of Hakon dying,
Sing his funeral wail!"
And another arrow flying
Grazed his coat of mail.

Turning to a Lapland yeoman,
As the arrow passed,
Said Earl Eric, "Shoot that bowman
Standing by the mast."
Sooner than the word was spoken
Flew the bowman's shaft;
Einar's bow in twain was broken,
Einar only laughed.

"What was that?" said Olaf, standing
On the quarter-deck.
"Something heard I like the stranding
Of a shattered wreck."
Einar then, the arrow taking
From the loosened string,
Answered, "That was Norway, breaking
From thy hand, O King!"

"Thou art but a poor diviner,"
Straightway Olaf said.
"Take my bow, and swifter, Einar,
Let thy shafts be sped."
Of his bows the fairest choosing,
Reached he from above;
Einar saw the blood-drops oozing
Through his iron glove.

But the bow was thin and narrow;
At the first assay,
O'er its head he drew the arrow,
Flung the bow away;
Said, with hot and angry temper
Flushing in his cheek,
"Olaf! for so great a Kamper
Are thy bows too weak!"

Then, with smile of joy defiant
On his beardless lip,
Scaled he, light and self-reliant,
Eric's dragon-ship.
Loose his golden locks were flowing,
Bright his armnor gleamed,
Like Saint Michael overthrowing
Lucifer he seemed.