Chapter One: The mamor begins with the verse of Esther (-9:27) and the teaching of our Sages (-Shabbos 88a), “Even so, they again accepted it (willingly) in the time of Ahasuerus, as it is written: ‘(The Jews) ordained, and took upon them, (and upon their seed, and upon all such as joined themselves unto them),’ (and he taught: The Jews) ordained what they had already taken upon themselves (through coercion at Sinai).
” Upon this the Previous Asks, how can it be that what the Jewish People did not accomplish (to accept the Torah uncoerced) at Mount Sinia, when they and the physical world were at the great heights effected by the Exodus of Egypt, they were able to accomplish in the darkness of exile by Haman?! The Previous Rebbe emphasizes the darkness of the exile was that Haman closed down the Torah schools for children, just as the evil king Achav did in the times of Isaiah, and Isaiah told Achav that you will not succeed in separating the children from the Torah.
--It is important to note that Stalin and the USSR regime did the same at the time this mamor was delivered, and the Previous Rebbe was non-stop going on self-sacrifice for the children's Torah-education, and demanded the same from his Chasidim.