Abstract: A covert and secure communication system which employs a very narrow bandwidth to permit receivers to be very sensitive to low power signals while maintaining acceptable signal-to-noise ratios. In the preferred embodiment, the system operates at the millimeter wavelength which, because of very high attenuation in atmosphere, will be undetectable beyond a very limited range. In another embodiment of the invention, the covert communication system is applied to an IFF system in conjunction with a homing missile. The IFF system of the present invention may be used as a back-up to confirm that a target is a foe by transmitting to and receiving a confirming signal from the target at the terminal portion of the engagement. For example, transmission between the target and missile may occur when the target and missile are less than 2,000 feet apart.