The rhetorical technique used in this excerpt is shift.
understatement.
logos.
parallelism

Shift

Explanation:

During the first four years of the last war the Allies experienced nothing but disaster and disappointment. That was our constant fear one blow after another, terrible losses, frightful dangers. Everything miscarried. And yet at the end of those four years the morale of the Allies was higher than that of the Germans, who had moved from one aggressive triumph to another, and who stood everywhere triumphant invaders of the lands into which they had broken.

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onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.

the purpose of the heading in the passage is to identify who is telling the story.

this excerpt is part of the book sugar changed the world (2010) written by marc aronson and marina budhos. as the book has been written by two people, the heading "marc" indicates that this specific excerpt is being narrated by aronson. in the fragment, marc describes his grandfather's story after hearing it from his cousin. however, there are other excerpts where budhos is the one that tells the story of her family.

aronson and budhos, who are husband and wife in real life, decided to write sugar changed the world when they found out how sugar, which had an important role in slavery and economy, changed their ancestors' lives.