A conceptual definition of combat effectiveness is an overall capability of a force to produce a desired outcome from a combat against an enemy force. An ability to measure combat effectiveness is critical to strategic and tactical decision making, but it is a challenging task to develop an operational measure for combat effectiveness due to large complexity presented by a rich context of a combat environment. We argue that under a direct fire engagement combat effectiveness can be reasonably assessed by the number of attack opportunities a force creates in a combat environment. This paper proposes a measure to quantitatively measure combat effectiveness of a military force in a direct fire engagement environment. The proposed metric is based on a meta-network representation that captures various aspects of a combat environment. Using a meta-network representation, two types of basic unit structures of attack opportunity - isolated and coordinated - are identified, which are then used as a basic element of combat effectiveness. Prevalence of network motifs in a networked combat environment is computed as a measure of a military force's combat effectiveness.