Chief Rabbis of Israel David Lau and Yitzchak Yosef have ruled that according to Jewish law, soldiers on the front line are exempt from fasting and other mourning practices on Tisha B'Av.
A Chief Rabbinate statement said, "In a prayer that the Holy One, Blessed be He, will guard them in their comings and goings to life and peace, may they be crowned with a crown of victory, and may we be privileged to see the consolation of Zion and Jerusalem with quiet and certainty."