Pierside combat systems training is a way to supplement the shore based training facilities and the at-sea exercises which are so necessary to keep a combat team at a high level of proficiency. This paper presents how pierside training is being accomplished with the use of the Device 20B4, Mobile Combat Systems Trainer. The 20B4 provides the capability for conducting individual operator and team training on the crew's ownship through stimulation of the installed operational equipment. The user can develop, modify, expand, and replay training exercises quickly through a combination of real-time and off-line software routines. The system presents a total electronic warfare environment to a wide range of sensors with a cost effective adaptability to the sensors and threats. The mobility of the 20B4 enables the system to be moved wherever the ships are located to achieve improved fleet readiness through realistic training and checkout.