Several years ago, I found a really interesting example that
illustrates how the country moved from an Unraveling to a Crisis era
in 1840.
The Crisis Era (Fourth Turning) begins when the previous Artist
generation completely loses influence in society, and that happens
almost unvaryingly and inexorably about 58 years after the climax of
the preceding crisis war. So WW II ended in 1945, and 58 years
later is 2003.
Here's an earlier example: The Revolutionary War climaxed in 1782, and
so the Fourth Turning Crisis era began 58 years later, in 1840.
In the 1840 time frame, here's an introductory description to
the Mexican-American war:
> The Mexican-American War (1846-1848) marked the first U.S. armed
> conflict chiefly fought on foreign soil. It pitted a politically
> divided and militarily unprepared Mexico against the
> expansionist-minded administration of U.S. President James
> K. Polk, who believed the United States had a “manifest destiny”
> to spread across the continent to the Pacific Ocean. A border
> skirmish along the Rio Grande started off the fighting and was
> followed by a series of U.S. victories. When the dust cleared,
> Mexico had lost about one-third of its territory, including nearly
> all of present-day California, Utah, Nevada, Arizona and New
> Mexico.
> Causes of the Mexican-American War
> Texas gained its independence from Mexico in 1836. Initially, the
> United States declined to incorporate it into the union, largely
> because northern political interests were against the addition of
> a new slave state. The Mexican government was also encouraging
> border raids and warning that any attempt at annexation would lead
> to war.
> Nonetheless, annexation procedures were quickly initiated after
> the 1844 election of Polk, who campaigned that Texas should be
> “re-annexed” and that the Oregon Territory should be
> “re-occupied.” Polk also had his eyes on California, New Mexico
> and the rest of what is today the U.S. Southwest. When his offer
> to purchase those lands was rejected, he instigated a fight by
> moving troops into a disputed zone between the Rio Grande and
> Nueces River that both countries had previously recognized as part
> of the Mexican state of Coahuila."
>
http://www.history.com/topics/mexican-american-war
So the United States completely reversed policy, becoming much more
belligerent with respect to Mexico between 1836 and 1844. In 1836,
America avoided war. In 1844, America was much more nationalistic,
ready to embrace war because of "manifest destiny." What changed?
What changed was the end of influence of the preceding Artist
generation, and the rise of the new Nomad generation, and that's the
beginning of America's Fourth Turning, or Crisis Era.