This timeline (admittedly more of a sketch than a fully fledged timeline at this point) was inspired by the recent thread on American intervention in the Franco Prussian War. Basically the POD is that Napoleon III supports the Union during the Civil War, and avoids getting entangled in Mexico.
ANSWERING THE CALL OF LAFAYETTE:
American Intervenes in the Franco-Prussian War
An Alternate History Timeline
by Robert Perkins
1861-1863--The American Civil War. In contrast to OTL, Emperor Napoleon III of France, following public opinion within France, throws his full support behind the Union. The government of Queen Victoria in Britain, influenced in part by Napoleon's diplomats, does likewise. Confederate arms purchasers are given the cold shoulder in both countries, and the war ends in April 1863 with the complete defeat of the Confederacy. Because the war goes much better for the Union right from the beginning, President Lincoln never issues the Emancipation Proclamation.
October 1861--Treaty of London. Britain, France and Spain decide to unite their efforts to collect unpaid debts from the Mexican government.
December 1861--Spanish fleet and army arrives at Vera Cruz.
1862--In Prussia, the largest of the German states, a member of the landed aristocracy, Otto von Bismarck, becomes Chancellor. Representing the king, he declares that his government is to rule without parliament.
January 1862--British and French fleets arrive at Vera Cruz.
March 1862--French army lands in Mexico.
April 1862--A convention of the London Treaty powers decides to withdraw from Mexico. Napoleon III, however, does not immediately go along with the other powers, and French troops remain.
May 5, 1862. The Battle of Puebla. French troops suffer a humiliating defeat at the hand of Mexican forces, although they do not suffer huge casualties.
June 1862--Upon learning of the defeat at Puebla, Napoleon III decides that Mexico might not be worth the effort it would take to seize it, and orders the withdrawal of French troops.
June 1862 onward--Recriminations in France over the defeat at Puebla lead to an earlier reform of the French military. Minister of War Jacques Louis Randon, with the approval of Emperor Napoleon III, closes loopholes in the national conscription regulations, and increases bonuses for reenlistment of veteran troops, both of which greatly increase the strength and quality of the French military.
April 1863 onward--At the end of the Civil War, relations between the United States and France are quite possibly better than they have ever been. In a speech before Congress in September 1863, President Lincoln publicly thanks Napoleon III for his support of the Union during the war, and for his respect for the Monroe Doctrine at a time when the United States was unable to directly enforce it. Over the upcoming years, relations between the two countries will continue to improve.
April 1863 onward--The process of Reconstruction proceeds in the United States. President Lincoln attempts to follow a relatively benign Reconstruction policy, and in an effort to regain the loyalty of the recently conquered Southerners, he sponsors a revival of the proposed 1861 Corwin Amendment to the Constitution, which guarantees that slavery cannot ever be abolished by action of the national government. However, the amendment is modified to also state that slavery cannot be introduced into any of the Territories of the United States, nor can it be adopted by any State in which it does not currently exist. In addition, the amendment specifically states that the right of secession from the Union does not exist. These benign policies, and especially the revival of the Corwin Amendment (now known as the Corwin/Lincoln Amendment), are vehemently opposed by Radical Republicans in Congress, and President Lincoln finds himself in a power struggle with Congress which effectively stymies the whole Reconstruction process.
January 1864--Based on the observations of French military attaches of the Union Army’s use of railroads during the Civil War, French Minister of War Jacques Louis Randon decides that railroads will play a crucial role in any future military crisis as the key to rapid mobilization. He hires the former head of the U.S. Military Railroad Bureau, Herman Haupt, who has recently left the U.S. Army and returned to civilian life, to assist in the design of a plan for the rapid mobilization of the French military. With the blessing of President Lincoln, Haupt goes to France, where his advice proves of great help to French planners.
February-October 1864--The Second Schleswig War proceeds as per OTL. Prussia and Austria emerge as the victors over Denmark. This gives further impetus to French military reform efforts, since French Minister of War Jacques Louis Randon can see that Prussia is an emerging military threat.
November 1864--President Lincoln narrowly defeats Democrat George B. McClellan (who is wildly popular as the General who captured Richmond in the summer of 1862) and is re-elected for a second term. At the same time, many of the most Radical Republican members of Congress are voted out by a weary public which wants a resolution for the Reconstruction issue.
March 1864 onward--The new, less radical Congress begins to cooperate with President Lincoln's Reconstruction proposals. By the end of 1864, all of the defeated Southern States have been re-admitted to the Union.
July 1864--Congress passes the Corwin/Lincoln Amendment. It is submitted to the States for ratification.
April 1865--Buoyed by the votes of the returned Southern States, the Corwin/Lincoln Amendment is ratified and becomes the law of the land as the 13th Amendment to the Constitution.
1866--The Seven Weeks War between Prussia and a coalition of Austria and several German states. Prussia inflicts a humiliating defeat on Austria and it’s allies, and effectively emerges as the new leader of Germany. France is still in the process of reorganizing and reforming it’s military, and, as in OTL, does not intervene in the war.
1869 onward--The states of the Upper South begin emancipating their slaves, starting with Delaware in 1869. By the end of the century, Maryland, Kentucky, and Missouri will have followed. Virginia, too, will consider emancipation legislation, but it’s legislature will vote it down by a narrow margin in 1898. Slavery remains strong in the Deep South, however, right up to the end of the century, with no sign of emancipation in sight.
1867--Jacques Louis Randon is replaced by Adolphe Niel as French Minister of War. Niel continues the reforms begun by Randon.
September 1868--Revolution in Spain overthrows Queen Isabella II.
November 1868--Presidential Elections in the United States. A Republican ticket consisting of war heroes Ulysses S. Grant and John C. Fremont handily defeats the Democratic challengers, George B. McClellan (still popular enough to be renominated by his party) and Samuel Tilden.
June 1870--The Spanish government offers the throne of Spain to Prince Leopold of Hohenzollern-Sigmaringen. This is vehemently opposed by France.
July 2, 1870--Prince Leopold of Hohenzollern-Sigmaringen withdraws his candidacy for the Spanish throne in response to French protests.
July 13, 1870--The Ems Dispatch. King Wilhelm I of Prussia is approached by the French ambassador while visiting the resort of Bad Ems. The French ambassador demands that the Prussian King guarantee that no Hohenzollern would ever again become a candidate for the Spanish throne. Wilhelm refuses. Later that day, he authorizes Chancellor Otto von Bismarck to release news of these events to the press. Bismarck, without changing the essential facts of the meeting, edits the press release in such a way that it appears to the French that the Prussian King insulted the French Ambassador, while at the same time appearing to the peoples of the various German states that the French Ambassador insulted the Prussian King.
July 19, 1870--France declares war on Prussia. The Franco-Prussian War begins.
July 1870-May 1872--The Franco-Prussian War (or, as it will be known in the United States, “The German War”). As in OTL, Prussia manages to persuade the south German states to join the war against France, and quickly mobilizes an army of over 1 million men for the invasion of France. The various reforms instituted in the French army since 1862 prove to be of great value, and France manages to mobilize nearly 800,000 well-trained men within a month after the declaration of war, with the goal of an ultimate mobilization of over one million men proceeding and well along toward completion. And, unlike in OTL, the mobilization is much better organized, thanks to the plan devised with the input of Herman Haupt. The French infantry is much better armed than the Prussians, although their artillery is, as in OTL, outclassed by the Prussian Krupp guns. However, the French are able to do much better in the early battles of the war, and although they do not win any outright victories, they manage to avoid any major defeats in the early months of the war, which bogs down into a bloody stalemate. Trench lines begin to scar the beautiful French countryside as both sides dig in.
The United States government, in response to French appeals, begins shipping surplus military equipment and other supplies to France almost immediately upon the declaration of war. The “yellow press” in the United States is meanwhile whipping up public opinion in favor of France, “our friend during the Great Rebellion, the land of Lafayette, now under the boot of the Teutonic bully.“ In response, the Prussians send out several commerce raiders which begin preying on U.S. shipping in the Atlantic and elsewhere. Public outrage over these depredations leads President Grant, on October 10, 1870, to ask Congress for a declaration of war on Prussia. Congress almost unanimously approves this declaration the next day.
The United States is able to mobilize more quickly than would otherwise be the case by calling upon it’s Civil War veterans…both Union and Confederate…who provide a large reserve of men with military experience and training who will form the core of the expanded army. Thus, within six months, the United States is able to form, equip, and transport to France, an American Expeditionary Force of 500,000 men (commanded by General William T. Sherman), with as many more in the process of training and equipage.
The structure of the American Expeditionary Force is as follows...
THE AMERICAN EXPEDITIONARY FORCE
General William T. Sherman, Army Group Commander
FIRST ARMY--General William Rosecrans
--1st Corps...Lt. General James Longstreet
--2nd Corps...Lt. General John Schofield
--3rd Corps...Lt. General George Meade
--4th Corps...Lt. General Winfield S. Hancock
Second Army--General Thomas Jonathan Jackson
--1st Corps...Lt. General Philip Kearny
--2nd Corps...Lt. General Ambrose Powell Hill
--3rd Corps...Lt. General James Ewell Brown Stuart
Cavalry Corps--Lt. General George Armstrong Custer
--1st Division...Major General Nathan Bedford Forrest
--2nd Division...Major General Judson Kilpatrick
Note that the First Army is composed primarily of brigades formed from Northern regiments. The Second Army (which is significantly smaller than the First Army) is composed primarily of brigades formed from Southern regiments.
The U.S. forces are armed with the various versions of the trapdoor Springfield Rifle (primarily Allin conversions of existing Civil War surplus muskets, which can be produced quickly and cheaply) at the outset, but President Grant soon contacts Oliver Winchester, who has acquired rights to the Spencer Repeating Rifle after purchasing the Spencer company in 1869, to have the Spencer mass-produced (Grant favors the Spencer design over Winchester’s own product, the Henry Rifle, because it fires a much more hard-hitting and longer-ranged cartridge). In cooperation with government arsenals, Winchester’s New Haven Arms Company, in cooperation with the various government arsenals and other private contractors, begins churning out Spencer Rifles by the hundreds of thousands by the end of 1871. By mid-1872, the American Expeditionary Force in France will be equipped almost entirely with the new Spencers.
The American Army is also equipped with batteries of another weapon...the Gatling Gun. Superior to the French Mitraleuse, the Gatlings are also accompanied by a better doctrine for their use than the one used for the French weapon, and overall, the Gatlings will be much more effective than the Mitraleuse during the war.
Units of American troops begin participating in the war well before the main American Army is deployed, with the first of these…an American cavalry division commanded by Major General George Armstrong Custer, with Nathan Bedford Forrest as one of his Brigadiers…taking part in battles in northern France as early as January 1871 (Custer will later rise to command the Cavalry Corps of the A.E.F., and Forrest to command one of the Divisions). However, they don’t begin to really make themselves felt until May 1871, at the Battle of Verdun, when a major offensive by American troops almost broke the German lines. However, they were inadequately supported by the French, and in the end, the amount of ground gained was not commensurate with the number of men lost.
Nevertheless, the weight of American manpower begins to tell, and from May 1871 until the end of the war two years later, the Germans are gradually forced back. The increased firepower which the Americans experience as a result of their gradual re-equipping with Spencer rifles, and their effective use of Gatling Guns also plays a significant role in this. By the Spring of 1873, the Germans have been pushed completely out of France and Franco-American forces are advancing into Germany itself.
Seeing the inevitability of defeat, in May 1873 King Wilhelm I of Prussia asks for the resignation of Chancellor Bismarck, which he receives. He then asks for an armistice. This is granted on May 16, 1873. Treaty negotiations then begin, mediated by the King of Belgium, at Brussels. They will drag on until August 1873.
November 1872--Presidential Elections in the United States. President Grant wins re-election over a Democratic Ticket consisting of Samuel Tilden and Andrew Johnson of Tennessee. Tilden and Johnson had run on a peace platform, citing the high casualties of the war in France. They lost by a landslide, and President Grant takes this as a mandate to continue the war to it’s conclusion.
August 1873--The Treaty of Brussels is signed between Prussia (representing itself and it’s allies), France, and the United States. By terms of this treaty, France is allowed to absorb Luxembourg, and receives a large indemnity from Prussia. Prussia also is forced to give up it’s control of the North German Confederation, with the complete sovereignty of the various German states within it to be recognized. German unification is effectively derailed.