Jefferson Davis's proclamation regarding the alleged crimes of US Major General Ben Butler in New Orleans, released shortly before Christmas in 1862, has to be one of the least seasonally appropriate communications ever issued by a Christian, at least since the 17th century Catholic-Protestant wars.
Davis's rage at Butler (who ironically had supported him for the US presidency in 1860), led him to threaten much worse things than the Union general had ever done. According to the proclamation, Butler and all officers under his command "be declared not entitled to be considered as soldiers engaged in honorable warfare but as robbers and criminals deserving death, and that they and each of them be whenever captured reserved for execution."
The same fate (implied but not quite spelled out) was promised to "all negro slaves captured in arms" and their officers. (This would have a considerable impact on the career of US Col. James Montgomery, whose biography I am currently writing.)
In the East, that December, the pall of Fredericksburg lingered.
Grant was frustrated in the early stages of his Vicksburg campaign, both by Confederate cavalry commanders Forrest and Van Dorn, and the financial dealings of his own father. On Dec. 17, he issued the notorious anti-Semitic order, but it was quickly overturned by Lincoln and repented of by Grant.
Still farther west, in the far corner of Arkansas, the news was better, in part due to Frank Herron.
And in Boston, at the end of the year, Frederick Douglass awaited Lincoln's issuance of the Emancipation Proclamation.
Update: If you think Jeff Davis's proclamation makes an unsuitable topic for the season, I will double down by linking to this post by Rod Dreher about the Armenian genocide and other grim matters, which is the best Christmas piece I've read this year.