1)
Why is there an Aleph after the Vov in "he'Halchu", and a Hei at the beginning?
1.
Radak, Malbim: We find like this elsewhere - "v'Lo Avu Shemo'a" (Yeshayah 28:12). Normally, the prefix Hei is not used with past tense to mean 'that', but there are exceptions, e.g. "ha'Hikdish Shmuel" (Divrei ha'Yamim 1 26:28).
2)
Why did Yehoshua tell the men who went with him to put their feet on the kings' necks?
1.
Malbim: This was a Siman that all [the kings] will fall under their feet. It was to invigorate them - "Chizku v'Imtzu" (verse 25).
