I'd give that more thought, and research masers a bit, before I decided to take a gun to a battlefield saturated with microwaves, or failed to use microwaves against enemies armed with metal guns during armed conflict.
Technology has progressed since chemical propellants were formulated, and firearms are much improved. Knives remain functional for many purposes, and no technology ever loses completely it's utility. Newer technology, such as DEW, isn't as publicly available for very good reasons.
Such as that people possessing it are practically immune from thugs. Those profiting from thuggery find that inconvenient.
If it does come to shooting, a pitched battle is a bad strategy against an established military or police force. Sabotage and subversion come first Guerrilla warfare is a potential last resort. Think Sun Tzu. Don't play to the opponent's strength.
I point out microwaves particularly for that reason. The strength of armies is numbers. One transmitter can obviate that advantage. Creating asymmetrical responses is the heart of Sun Tzu.