Published in 1977, Bu is distinguished by two features nearly unique in all of wargamedom.
Units are battalions or regt.
EX uses printed defense strength vs. printed attack strength. Displacement and advance after combat allowed. Arty can barrage, must attack adjacent enemy units and can use FPF to supplement another defending unit. Ground support points used as FPF and barrage in same turn. 22 bridges can be demolished by Nato with dr.