The territory of the tribe of Gad guarded the border of the Land of Israel. Moses therefore blessed this tribe with military valor.
Battling Intimidation and Hesitation
וּלְגָד אָמַר . . . כְּלָבִיא שָׁכֵן וְטָרַף זְרוֹעַ אַף קָדְקֹד: (דברים לג:כ)
[Moses] said of the tribe of Gad, “May he dwell like a fearsome lion, tearing off the arm and the head [of its prey in one blow].” Deuteronomy 33:20

Our physical conquest of the seven nations who occupied the Land of Israel alludes to our spiritual conquest of the seven emotions of the human/animal soul. The two major obstacles to this conquest are the “arm” and the “head.”

The “head” is the mental block that results from calculating the odds of success against the dominant material culture. Confronted with the overwhelming resources commanded by materialistic society, the lone Jew is tempted to give up before even beginning the fight. The “arm” is our physical resources we have at our disposal. We have worked hard to earn these resources, and are therefore reluctant to expend them on spiritual pursuits whose material benefits are not at all apparent.

We must therefore deny the validity of both these attitudes together, “in one blow.”1