Once these cities are raised to the ground, the buildings have fallen down, it is almost impossible for attackers to gain a foothold. the russians know all about this from the second world war. over 1 million red army soldiers, dying, defending stalingrad. but what happened in syria is that after a four year, conventional battle for aleppo, in northwest syria, in december 2016, and 13 days, they dropped chlorine barrel bombs to break that siege. the chlorine seeps underground, it's it's heavier than air, and people hide in rubble, and underground. the chlorine either killed from underground, o...