A company is a military unit which usually has from 80 to 250 soldiers. A company is usually led by a captain or a major. Most companies are made up of from three to six platoons, although the exact number may vary by country. Several companies are grouped to form a battalion or regiment. In the United States military, before the September 11 attacks, companies trained in conventional warfare for basic offensive and defensive operations. Since then companies have had to train for a much wider variety of tasks. These may include humanitarian aid missions, providing security and maintaining order in an area. Different elements in an army may assign different tasks or have different names for a company. For example, a corps of engineering such as the Royal Engineers use the term squadron for a company. In other examples, the name company may be replaced by the name battery.