
Radical Democrats denounced the war and opposed action of Federal authorities.

They were called “Copperheads” because of the emblems they wore.

Many were brought to trial and imprisoned.
Clement Vallandigham was arrested and banished to the Confederacy.
High Lights of History: The “Copperheads”
By J. Carroll Mansfield
North Adams Transcript(North Adams, Massachusetts) Dec 30, 1927
Read more about the Copperheads: The Traitorous Copperheads (“Peace” Democrats)

Image from the Son of the South website, which has tons of great images and information.
Here are a couple of “Copperhead” poems:
A SOUTHERN CALL ON NORTHERN COPPERHEADS.
“RALLY, SNAKES.”
Come out, you slimy hussies,
Forget domestic musses,
And vend a few more cusses
On Abolitionists.
Wake, snakes!
Vallandigham will lead you,
While Southern traitors feed you;
And, Oh! how bad we need you,
‘Gainst Abolitionists.
Wake, snakes!
There’s only one condition,
To save us from perdition,
Just stop this Abolition —
D—-d Abolition.
Wake, snakes!
There’s nothing you can do, sirs,
To help both us and you, sirs,
Like making much ado, sirs,
‘Pout Abolition.
Wake, snakes!
The Athens Messenger (Athens, Ohio) Sep 17, 1863

[For the Messenger.
COPPERHEADS — A PARODY.
___
BY ISAAC PARTINGTON.
___
The beams of peace were smiling o’er,
Each lovely valley, hill and moor,
As through a Northern village came.
A man, with, on his brow, his name —
A “Copperhead.”
His brow was sad, with look forlorn,
His long, neglected beard, unshorn,
And with each breath he heaved a sigh —
A tear was glistening ‘neath the eye,
Of Copperhead.
A happier man he once had been,
He never dared to stoop to sin;
But love his country ever free,
And thought not that he e’er could be
A Copperhead.
But when secession clouds came o’er,
The tempter whispering at his door,
His mind and reason, so estranged,
That ere a twelvemonth he is changed,
A Copperhead.
“Oh don’t forsake,” his wife did plead,
“Your country in her hour of need.”
But putting all advice aside,
With fiendish look, “I’ll be, he cried,
“A Copperhead.”
“Beware! beware!” his conscience said,
“A day of reckoning’s o’er your head;
Your country’ll through this chastening rise,
And pour out vengeance from the skies,
On Copperheads.”
But heedless, quite, his way he took,
And all his former views forsook.
With hiss and sting he now was found,
The vilest reptile ‘bove the ground —
A Copperhead.
Too great a coward to go and fight,
To gain his “Southern brethren’s” right,
He stayed at home, with tongue and pen,
He hisses at our Union men —
Vile Copperhead.
But when the blast of war was gone,
And peace again our land smiled on,
The branded curse upon his brow,
No rest would Freedom’s soil allow,
To Copperheads.
And so this man now wanders forth,
He’s cursed, all round from South to North.
A second Cain. Such is the fate,
That in the future does await
All Copperheads.
The Athens Messenger (Athens, Ohio) May 28, 1863