The phrase "heavy arms attack" refers to a military strike involving powerful and destructive weapons. Synonyms for this phrase could include "heavy artillery assault," "armed assault," "weaponized aggression," or "heavy weapon barrage." Another option could be to specify the type of weapon used, such as a "missile strike" or "bombing raid." These synonyms convey the same sense of forceful and overwhelming attack, with different nuances in the type of weaponry utilized. In any case, a heavy arms attack is a serious and violent military action that can have far-reaching consequences for all involved.