Military development and trade have long been connected through the production and consumption of raw materials and goods needed to support militarism, protection from other aggressive polities, and human labor. In order for a given society to develop sufficiently to become a dominant military power, that society needs an ample, regular supply of a wide range of resources and goods. In addition to basics such as food and clothing, military forces need transportation and arms.
In ancient times, animals were primarily used for land travel, while ships were essential for maritime forces. Materials such as wood for construction and various metals for weapons and armor were often obtained from other, far-off societies. Specialized or luxury goods also played prominent roles; in various world areas, precious metals and gems, unusual consumables such as tobacco, and finely crafted or art objects have been tightly controlled by elites.
To ensure these supply chains were not interrupted, the more heavily militarized societies offered protection to their trade partners; such support included fortifications they constructed as well as the occupying forces that were stationed at outposts and strategic points along trade routes or accompanied the trading caravans. The vast labor needs of the militarized societies were often provided by the subjugated peoples, sometimes through the imposition of conscription or even slavery.