Why does it mention giving their land to Yisrael?
Radak: Yisrael are the chosen among all the nations; He gave to them a land chosen over all lands.
Malbim: There were many new miracles in Yehoshua's war [to conquer the land]. This was not in order that I recognize Hashem's deeds. Rather, it is because this is Yisrael's inheritance that Hashem gave to the Avos due to his love for them, so He strove 1 that they take what they deserve.
Why did he say 'Hishtadel'? Perhaps it is because Yisrael had choice to reject their inheritance (like the Meraglim's counsel) or accept it. Had the war been natural (Ramban (Bamidbar 14:9) says that Yehoshua and Kalev said that due to the Kena'anim's fear of Yisrael, we could defeat them naturally), Yisrael would have been more prone to reject the land. (PF)
