Which policy was a last-ditch effort by the US Congress to preserve the Union and stave off secession

The answer is the Compromise of 1850. This compromise wanted to stop the secession conflicts that were happening in the US. The said law was able to diffuse the on-going conflicts with regards to the lands acquired from the Mexican-American War. It was able to stop some issues of the ongoing crisis but citizens have different opinions with regards of this law

Explanation:

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relations between the soviet union and the united states were driven by a complex interplay of ideological, political, and economic factors, which led to shifts between cautious cooperation and often bitter superpower rivalry over the years. the distinct differences in the political systems of the two countries often prevented them from reaching a mutual understanding on key policy issues and even, as in the case of the cuban missile crisis, brought them to the brink of war.

the united states government was initially hostile to the soviet leaders for taking russia out of world war i and was opposed to a state ideologically based on communism. although the united states embarked on a famine relief program in the soviet union in the early 1920s and american businessmen established commercial ties there during the period of the new economic policy (1921–29), the two countries did not establish diplomatic relations until 1933. by that time, the totalitarian nature of joseph stalin's regime presented an insurmountable obstacle to friendly relations with the west. although world war ii brought the two countries into alliance, based on the common aim of defeating nazi germany, the soviet union's aggressive, antidemocratic policy toward eastern europe had created tensions even before the war ended.

during the ming dynasty