This week's featured article at the Sobel Wiki is on the Rocky Mountain War, which is pretty much the central event in For Want of a Nail... (and I'm not just saying that because I wrote half a dozen For All Nails vignettes about the war). As Sobel says in the first paragraph of his preface, the United States of Mexico and the Confederation of North America are more than neighbors, they're more like cousins. They were both offspring of the American Revolution (or, as it's known in the Sobel Timeline, the North American Rebellion), but they took different paths afterwards. You could say much the same thing about our world's U.S.A. and Canada, but those two countries are, as Trudeau famously observed, like a mouse beside an elephant. Sobel created a world where the Patriots and the Loyalists each got their own country, and the two countries were an even match for each other.
"Robert Sobel", the Australian business historian who is the nominal author of Nail, is a firm believer in the idea that the two nations are natural enemies, have always been so, and will always be so. He plays this theme up throughout the book, in spite of considerable evidence in the narrative that it isn't so. To cite one instance, Simon Cardenes, Mexico's leading author in the late 19th century, is also a particular favorite among North Americans, and when Mexican dictator Benito Hermión names him the U.S.M.'s ambassador to the C.N.A., Sobel lauds Hermión for making an excellent choice.
But there are a few instances where the two countries are genuinely hostile to each other, and the Rocky Mountain War is the most serious one. It's an eight-year-long all-out war between the two countries, and "Robert Sobel", the anti-Mexican ideologue, makes the most of it. Chapter 11, "California Gold", ends with a growing series of border clashes between the two countries in the late summer of 1845. Chapter 12, "The Rocky Mountain War", sees the clashes grow into full scale war between the two countries, as the C.N.A. carries out a series of invasions of the U.S.M., each more costly than the last. The chapter ends with growing popular opposition to the war in both nations resulting in the election of peace candidates in each. Chapter 13, "The C.N.A.: The Corruption of Progress", begins with the two national leaders agreeing to a truce in the summer of 1853, with the signing of a peace treaty two years later.
The war is a defining moment for both countries. The cost of the war permanently sours the people of the C.N.A. on imperialism, and the country becomes isolationist and pacifistic, even as the world's other major powers are swept up in a constant struggle for overseas colonies that ends in worldwide war in the 20th century. For the Mexicans, the war has the opposite effect. The territorial losses suffered in the peace agreement, minor though they are, cause the U.S.M. to become steadily more militant over time, carving out a colonial empire that includes much of South America and a significant section of Asia, culminating in an unprovoked attack on Japan in 1942.
For Want of a Nail... ends in 1971, with the C.N.A. and U.S.M. seemingly replicating the slow descent towards war of the 1840s. The discovery of a Mexican spy ring in the C.N.A. in 1969 causes the two nations to break off relations and close their borders, and guerrilla activity has begun to break out along the long border. In For All Nails, the two nations achieve a detente, and even form a tentative military alliance in the mid-1970s, but I don't think that's how Sobel meant the story to end.