Spartan hoplite. Print from Vinkhuijzen Collection of Military Costume Illustration. (Photo credit: Wikipedia)
In ancient Greece, the most useful and powerful type of soldier was the hoplite. This was a soldier who was armed with a long spear, and who, with his other mates in his squadron, formed together in a formation called the Phalanx Formation, in which all the hoplites in that squadron (of which there were about 20 per squadron, or unit) formed into a square, marching cose together with the front row having their shields almost overlapping, and their spears bristling out from between the shields, a bristling wall to advance upon the enemy.
Because it would be practically impossible to keep formation while running, the unit could not move very fast, and so the Hoplites would be subceptible to archers. Without their armour or shield, that is.
The hoplite’s armour and equipment was valuable to the hoplite, worth both money and a symbol of the hoplite’s honor (keep in mind that the hoplites were the “elite” the best of the best, and slaughterers of the persian forces at Thermopylae), in fact, losing your shield means dishonor and shunning from freinds and family. Anyway, the most precious things the Hoplite used were the helmet, breastplate, spear, and shield.