A typical, tactical architecture for the comparative evaluation of the key design issues for coherent beam combining (CBC) and incoherent beam combining (IBC) is shown in Fig. 1. Fan surveys current methods under study for beam combining.6 Possible combination methods of multiple laser sources vary, but those methods applicable for tactical power levels can all be classified as either coherent or incoherent.3,6 All proposed beam combination methods can be readily adapted to an architecture that uses a single beam director, i.e., a gimbaled telescope, for beam projection5 as shown in Fig. 1. The architecture shown in Fig. 1 is considered the most practical and cost effective for the capabilities required to project a multilaser source in the case of either coherent or incoherent beam combining. This architecture allows for a direct comparison of coherent and incoherent combination without requiring new invention and its associated complexity. The beam director both transmits and receives allowing for proven solutions to pointing, tracking, and adaptive optics. Essentially, this architecture is an incremental change to any previously proposed DE tactical systems that would use a single source, but the design in this work presumes a multilaser source. Other approaches for IBC have proposed individual trackers, adaptive optics, and beam directors as a possible architecture.4 The analysis within this paper is general enough to include this approach. The on-axis beam expander precludes a subaperture source on axis and, thus, reduces the fill factor (later defined in detail) leading to a reduction in propagation efficiency (also, defined shortly). However, the architecture is proposed as a design increment towards an optical phased array system which requires coherent transmitting and receiving,12,16 through individual beam directors for each source element. In this respect, the paper concentrates only on the use of multilaser sources and directly compares the performance metric of propagation efficiency for the cases of incoherent and coherent beam combining. Less ambitious than an optical phased array system, this architecture has the advantage of lower cost with less technology development required for such a system and provides an intermediate look at the issues and advantages of phasing the source.