their guns are usually grouped in teams called either "crews" or "detachments". Several such crews and teams with other functions are combined into a unit of artillery, usually called a battery, although sometimes called a company. In gun detachments, each role is numbered, starting with "1" the Detachment Commander, and the highest number being the Coverer, the second-in-command. "Gunner" is also the lowest rank, and junior non-commissioned officers are "Bombardiers" in some artillery arms. Batteries are roughly equivalent to a company in the infantry, and are combined into larger military organizations for administrative and operational purposes, either battalions or regiments, depending on the army. These may be grouped into brigades; the Russian army also groups some brigades into artillery divisions, and the People's Liberation Army has artillery corps. The term "artillery" also designates a combat arm of most military services when used organizationally to describe units and formations of the national armed forces that operate the weapons. Tactics During military operations, field artillery has the role of providing support to other arms in combat or of attacking targets, particularly in-depth. Broadly, these effects fall into two categories, aiming either to suppress or neutralize the enemy, or to cause casualties, damage, and destruction. This is mostly achieved by delivering high-explosive munitions to suppress, or inflict casualties on the enemy from casing fragments and other debris and from blast, or by destroying enemy positions, equipment, and vehicles. Non-lethal munitions, notably smoke, can also suppress or neutralize the enemy by obscuring their view. Fire may be directed by an artillery observer or another observer, including crewed and uncrewed aircraft, or called onto map coordinates. Military doctrine has had a significant influence on the core engineering design considerations of artillery ordnance through its history, in seeking to achieve a balance between the delivered volume of fire with ordnance mobility. However, during the modern period, the consideration of protecting the gunners also arose due to the late-19th-century introduction of the new generation of infantry weapons using conoidal bullet, better known as the Minié ball, with a range almost as long as that of field artillery. The gunners' increasing proximity to and participation in direct combat against other combat arms and attacks by aircraft made the introduction of a gun shield necessary. The problems of how to employ a fixed or horse-towed gun in mobile warfare necessitated the development of new methods of transporting the artillery