Continuing the alt-hist theme from the last post.
The American Civil War seems to be a favorite what-if area for a lot of novelists, and I suppose for good reason. It was the first 'modern' war. When it started, the Union and the Confederacy fought in the line-up and charge that armies had used for the previous 100 or so years. By the end, both sides were developing the awful tactics and living conditions of trench warfare.
One side was fighting to maintain a strong federal union, the other for the rights of individual states to decide their own affairs. The Confederate States were a bit more 'decentralized' than the United States were. Although the institution of slavery was certainly a hot-button issue, it wasn't the primary reason by itself that the South seceded. No one has ever yet convinced me that slavery would have survived the introduction of mechanical cotton processing machinery-why always feed and care for a lot of people when you can invest in a machine that won't consume anything when not in use? To use the old line from The Godfather: "It isn't personal. It's just business." I don't think the plantation owners were a particularly evil bunch in that respect. But I digress.
One theme that alternate history authors commonly use is 'What if Britain had entered the Civil War on the Confederate side?' Robert Conroy uses this plot point in the novel 1862, as did Harry Harrison in the Stars and Stripes Trilogy (Not good. Harrison has written much better).
It sounds like a promising point. Britain was neutral but inclined toward the Confederate States. The CSA was counting on British textile mills needing Southern cotton. What Britain ended up doing was developing the Egyptian and Australian cotton industry instead, and selling arms to the CSA. Perhaps, had the Confederacy won at Gettysburg or Vicksburg or enough times on the way to the 1864 US presidential election-piling up enough wins to give the Union pause, kick Lincoln out of office, and put in someone to sue for peace with the CSA, then Britain may have stepped in with massive aid for the South.
I have a problem with the concept most authors cling to, though, that Britain would have had massive forces to send to fight the US on its home turf. Certainly the Royal Navy was sizable-but so was the US Navy. It was a pivotal time in naval warfare and shipbuilding, and both sides would have an odd assortment of sailing ships, steam vessels, armored ships, and ironclads. The US Navy would have been deployed in a defensive position along the coasts, while the Royal Navy had to protect the sealanes of the world and defend its far-flung possessions. The British would, of course, be able to concentrate a force to break through the US blockade of its own coast-but it would have to spread out its forces to prevent the US from raiding its commerce and colonies at the same time. Not as easy as it sounds.
The British Army has traditionally been a small force and even in the glory days of the Empire, was spread out over half the world. In many locations the British Army consisted of 'native' regiments led by British officers. Although the Army could use Canada as a base to attack the Union, it would have had to cross the Great Lakes-no transcontinental railroad in Canada to rapidly move troops-or base in Vancouver to attack the West Coast-likely San Francisco. I personally don't believe the British Army or Royal Marines could conquer the US, but they could have captured and raided some of the coastal cities. To think that the combined British-Confederate forces could have captured the whole of the US is to see those two armies swallowed up in the Allegheny and Sierra Nevada mountain ranges. North America is a vast place and an invading force could get swallowed up in the landmass. You could ask the Wehrmacht about getting swallowed up in a great open land, were it still around after getting used up in Russia.
Speaking of whom...
Most of the major European powers were watching events in North America in the 1860s. France was embroiled in its own adventure in Mexico at the time and would probably have preferred a friendly Confederacy on its northern border instead of the United States and the Monroe Doctrine (basically, Europe, stay the hell out of affairs in the Western Hemisphere that don't concern your colonies in the region), which is what actually happened. Russia was inclined toward the United States-Tsar Aleksandr II had liberated his own serfs in 1860-and sent warships to New York Harbor. Prussia and Austria were inclined toward the Union but probably not enough to bother going to war with Britain and France. While Britain of the 1860's had few men recognized as great generals or admirals, it did have some adept diplomats. They evidently knew enough to play the waiting game, not piss off any of the other powers, shake hands with the winner, and send condolences to the loser.
My thoughts, for what they're worth. I conclude that European aid to the Confederacy could have hurt the Union cause. British and French troops could have conducted amphibious assaults on places like San Francisco, Boston, New York, and Philadelphia. But if an author tells you that the British and French would land a force of 100,000 men to capture the US in the Civil War, here's what I'd do to defeat that plot:
-Move the national capital to Pittsburgh.
-Let the invading army drive past a hollow screen of forces and draw them into the Appalachians and Alleghenies.
-Turn Grant or whoever is competent loose to grind the invading force into dirt and block the passes where practical. I'll have interior position so I can shuttle troops back and forth where needed-no air power to bomb the rail net. Plus I have the whole of the continent to retreat into.
-Make nice with the Russians, Prussians, and Austrians. See who'll ally with us and open a second front in Europe.
The 'what-if' of European intervention in the Civil War probably makes for good reading for an afternoon-though I prefer The Guns of the South, where white-supremacist South Africans travel back in time and introduce the AK-47 to the Confederate Army. But when you dig deeper into the politics of the era, events probably played out 'correctly'. I think Britain probably had everything thought out about the same as I do and said "Ahh, President Davis. Look, you're going to have to show us a bit more staying power. But we do have a warehouse of Enfield rifles for you, if you can get a way to get them to your homeland yourself. Just send us gold. Your money's no good here."