Why did the growth of cities lead to the expansion of trade?

With the growth of cities, commodity-market relations developed – the larger the city and the number of its inhabitants became, the more difficult it was to provide oneself with food and necessary household items. Following from this, people tried to buy what was missing in neighboring cities and environs, to exchange for what they produced themselves (demand is a consequence of supply). With the expansion of settlements, the production of goods began to increase, artisans and merchants flocked to the cities. The division of labor began to develop – professions, crafts, agriculture, cattle breeding appeared. The workers began to unite in guilds. The very construction and expansion of cities also required materials for construction – thus trade began to develop. Traders sold their own “product”, trade rapidly “spread” to nearby cities, and competition emerged.