What sacrifices did Stalin make during World War II, that the allies didn’t have to make, that made Stalin think that his country had earned the future control of Eastern Europe?

the answer would be logic.

frederick william of brandenburg-prussia trained his son, frederick, to be a hardy soldier. but frederick disliked rifle shooting and horseback riding. unlike his father, he was interested in french literature. he enjoyed poetry and music and, like some others of the enlightenment, he scoffed at religion. his father thought him soft, frivolous and unmindful of his duties. and when frederick refused to put his signature on a right to succession, for a few moments his father strangled him.

how did the pendleton civil service act weaken the spoils system after president garfield died?

the act forced federal employees to pass competitive exams.

the act said that federal employees could be fired for political reasons.

the act said that company contracts and kickbacks were illegal.

the act stopped the reform movement in its tracks.

i believe it would influence their own way of understanding things. it shall be a foundation where they can draw or start an argument.   historians are also  scientists that  have their tools of analysis and expertise to unlock a variety of difficulties such as relationships of man, origin, politics, economy, and culture. based on facts and understanding on these areas, they may shade light to extract ideas and develop options to validate a hypothesis or debunk it.