From the end of parshat Ki Teitzei:
mevushav, which he did not expect and was thus unfair, with trickery in the even vaaven, and finally with Amalek, as a reason for finishing them off.
I would suggest that there is a different theme at play here, either in place of the other, or as an addition. Namely, at the time, the Israelites were not able to stand up for themselves, for their own honor, and for the honor of Hashem. Why? Because at that time they were "faint and weary." But once they get settled -- בְּהָנִיחַ ה אֱלֹהֶיךָ לְךָ מִכָּל-אֹיְבֶיךָ מִסָּבִיב, בָּאָרֶץ אֲשֶׁר ה-אֱלֹהֶיךָ נֹתֵן לְךָ נַחֲלָה לְרִשְׁתָּהּ -- then, they are to turn around and settle the score with Amalek. I think the contrast between the two pesukim is deliberate.