In the Greco-Roman era, warfare was up-close, sanguinary, and lethal. The Greeks and Romans, who were the masters of warfare, often employed the phalanx—a military formation consisting of rows of heavily armored soldiers with full-body shield and spear. A single soldier who was not in this formation was very vulnerable in battle; the chances of him deserting the battlefield were very high. The phalanx, therefore, was a reassuring source of protection and courage. It was a very simple formation–one simply lined up, with comrades to the left and right–but it proved to be overwhelmingly effective, as this formation allowed Alexander the Great to defeat armies that were over twice their size, taking over the known world.