It is a comment about the law that says we are forbidden from cutting down a fruit tree in the midst of war and siege. The teaching is all the more poignant as war permeates the days and nights of the middle east.
The fruit tree of the field during war stands as a memorial to a very special and important tree in the history of the world...the Tree of Life in Gan Eden...it stands as a reminder to what the world once was, of a time when harmony, peace and perfection were tangibly present in this world...seeing the fruit tree during wartime, which itself is a sign and a result of the downfall of humankind since we were forced to leave Gan Eden, is meant to move the heart of the soldiers on the battlefield, to pause for a moment and to lift their heads up above the reality of conflict and fighting that they and their people (and all peoples) are enslaved to, and remember that there once was a time when things were different, things were better...this remembrance, even if for but a few seconds, can give those fighting on the battle field of yet another war the hope and the belief that such a reality will return to Earth once again...may it be in our lifetime...
the teaching continues with this beautiful thought...that there is an example of Hashem (God) also keeping this mitzva of bal tashchit in the Torah...where?...after the flood of Noah's generation...how do we know?...because the dove comes back with a living branch from an olive tree...how did this olive tree survive the destructive waters of the Flood?...because Hashem kept [the law of] bal tashchit [do not destroy the fruit trees] and didn't harm the trees!...he quotes a Hazal (the traditions of the rabbis of old) that say that the waters of the flood soaked the Earth only to the level of the roots of the vegetation, but not of the trees...amazing...
May this teaching indeed bring hope to all who are forced to fight.