reporter: retired army general michael repass says artillery could blunt the russian offensive. the artillery that we re giving them is a method to counter that artillery fire that the russians are pouring on to the ukrainian troops, and also to the civilian communities. reporter: the russian plan calls for sending some 90,000 troops to encircle the ukrainian army in the east. artillery plus real-time battlefield intelligence provided by the u.s., could give the ukrainians a fighting chance. battlefield math holds that the offense needs a three-to-one advantage over the defense in order to break through. right now, the russians do not have a three-to-one advantage in eastern ukraine. norah. o donnell: that s some significant reporting. david martin, thank you. let s turn now to some breaking news. the department of justice is moving to reinstate the transportation mask mandate at the request of the c.d.c. this is setting the country up for a legal showdown. cbs errol barnett i