Greek hoplite warfare has traditionally been explored through the extant textual and pictorial evidence. This has resulted in an incomplete picture, with much of the focus on the strategic and tactical aspects of battle, to the neglect of practical and functional considerations of combat. As a consequence, many of our understandings of the nature of hoplite combat, the how, remain deficient. In this paper, I explore the structural and functional aspects of the hoplite shield, the single most important item in the Greek hoplite's panoply, to determine its efficacy in a combat environment. Through a set of controlled practical experiments, the effectiveness of the hoplite shield is tested to establish its defensive qualities vis-a-vis the long thrusting spear, the hoplite's primary offensive weapon. Hayward (1968, 316) defines combat effectiveness as 'the probability of success in combat operations'. Consequently the combat effectiveness of the hoplite shield can be determined by establishing the probability of achieving success (defending/ striking an opposing hoplite) in a combat environment.