Arguably, your claim may stretch too far. It may possibly be shown that Confederate independence was shown without showing the establishment of full diplomatic relations.
Right after the events at Fort Sumter, Lincoln declared a blockade of the ports of the deep South. Almost immediately, Great Britain declared its neutrality.
Lincoln soon declared a blockade of the ports of the upper South.
In his special message of July 4, 1861, one may see Lincoln revising the history of what he had done: "a proclamation was issued for closing the ports of the insurrectionary districts by proceedings in the nature of Blockade." In point of fact, Lincoln had twice announced a blockade with no mention of any closing of the ports.
A closing of the ports is a domestic action. A blockade is an international action. The recognition of Confederate independence arose with the British declaration of neutrality. In international law, neutrality was defined as "The state of a nation which takes no part between two or more other nations at war with each other."
Not until the war was won was it possible to truly admit the error and correct it and actually announce a closing of the ports -- on April 11, 1865. At the time of this proclamation, Secretary of the Navy Gideon Welles said: "This was a step which I had earnestly pressed at the beginning of the rebellion, as a domestic measure, and more legitimate than a blockade, which was international, and an admission that we were two nations."
It could be argued that the British declaration of neutrality (and all other such declarations of neutrality declared by other nations) recognized the CSA as an independent nation, flowing from Lincoln's proclamation of a blockade which, no doubt unintentionally, proclaimed to the world Lincoln's admission that the CSA was a separate nation.
Bouvier's Law Dictionary, 1856 Edition
NEUTRALITY, international law. The state of a nation which takes no part between two or more other nations at war with each other.
2. Neutrality consists in the observance of a strict and honest impartiality, so as not to afford advantage in the war to either party; and particularly in so far restraining its trade to the accustomed course, which is held in time of peace, as not to render assistance to one of the belligerents in escaping the effects of the other's hostilities Even a loan of money to one of the belligerent parties is considered a violation of neutrality. 9 Moore's Rep. 586. A fraudulent neutrality is considered as no neutrality.
3. In policies of insurance there is frequently a warranty of neutrality. The meaning of this warranty is, that the property insured is neutral in fact, and it shall be so in appearance and conduct; that the property does belong to neutrals; that it is or shall be documented so as to prove its neutrality, and that no act of the insured or his agents shall be done which can legally compromise its neutrality. 3 Wash. C. C. R. 117. See 1 Caines, 548; 2 S. & R. 119; Bee, R. 5; 7 Wheat. 471; 9 Cranch, 205; 2 John. Cas. 180; 2 Dall. 270; 1 Gallis. 274; Bee, R. 67.
4. The violation of neutrality by citizens of the United States, contrary to the provisions of the act of congress of April 20, 1818, 3, renders the individual liable to an indictment. One fitting out and arming a vessel in the United States, to commit hostilities against a foreign power at peace with them, is therefore indictable. 6 Pet. 445; Pet. C. C. R. 487. Vide Marsh. Ins. 384 a; Park's Ins. 'Index, h. t.; 1 Kent, Com. 116; Burlamaqui, pt. 4, c. 5, s. 16 & 17; Bunk. lib. 1, c. 9; Cobbett's Parliamentary Debates; 406; Chitty, Law of Nat., Index, h. t.; Mann. Comm. B. 3, c. 1; Vattel, 1. 3, c. 7, SS 104; Martens, Precis. liv. 8, c. 7, SS 306; Boucb. Inst. n. 1826-1831.
OFFICIAL RECORDS: Series 3, vol 5, Part 1, page 107
(Union Letters, Orders, Reports)
VII. April 11, 1865.-Closing certain ports.
BY THE PRESIDENT OF THE UNITED STATES OF AMERICA:
A PROCLAMATION.
Whereas, by my proclamations of the nineteenth and twenty-seventh days of April, one thousand eight hundred and sixty-one the ports of the United States in the State of Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, and Texas were declared to be subject to blockade; but whereas, the said blockade has, in consequence of actual military occupation by this Government, since been conditionally set aside or relaxed in respect to the ports of Norfolk and Alexandria, in the State of Virginia; Beaufort, in the State of North Carolina; Port Royal, in the State of South Carolina; Pensacola and Fernandina, in the State of Florida, and New Orleans, in the State of Louisiana;
And whereas, by the fourth section of the act of Congress approved on the thirteenth of July, eighteen hundred and sixty- one; entitled "An act further to provide for the collection of duties on imports, and for other purposes," the President, for the reasons therein set forth, is authorized to close certain ports of entry:
Now, therefore, be it known that I, Abraham Lincoln, President of the United States, do hereby proclaim that the ports of Richmond, Tappahannock, Cherrystone, Yorktown, and Petersburg, in Virginia; of Camden (Elizabeth City), Edenton, Plymouth, Washington, New Berne, Ocracoke, and Wilmington, in North Carolina; of Charleston, Georgetown, and Beaufort, in South Carolina; of Savannah, Saint Mary's, and Brunswick (Darien), in Georgia; of Mobile, in Alabama; of Pearl River (Shieldsborough), Natchez, and Vicksburg, in Mississippi; of Saint Augustine, Key West, Saint Mark's (Port Leon), Saint John's (Jacksonville), and Apalachicola, in Florida; of Teche (Franklin), in Louisiana; of Galveston, La Salle, Brazos de Santiago (Point Isabel), and Brownsville, in Texas, are hereby closed, and all right of importation, warehousing, and other privileges shall, in respect to the ports aforesaid, cease, until they shall have again been opened by order of the President; and if, whole said ports are so closed, any ship or vessel from beyond the United States, or having on board any articles subject to duties, furniture, and cargo, shall be forfeited to the United States.
No, I'll stand by my position that not a single nation recognized southern independence, or considered it to be a sovereign nation and that included the Lincoln Administration. The universally accepted standard for sovereignity is acceptance of that fact by the other nations of the world. Not a single nation bestowed official recognition of the Davis regime as the legitimate government for the southern state. Every government in the world viewed the Civil War as what it was, a rebellion, a domestic issue for the U.S., and refusing to take sides did not automatically convey recognition.
Let's quote some more of that.
"This is essentially a people's contest. On the side of the Union, it is a struggle for maintaining in the world, that form, and substance of government, whose leading object is, to elevate the condition of men -- to lift artificial weights from all shoulders -- to clear the paths of laudable pursuit for all -- to afford all, an unfettered start, and a fair chance, in the race of life. Yielding to partial, and temporary departures, from necessity, this is the leading object of the government for whose existance we contend."
A. Lincoln 7/4/61
Walt