A quick attack, particularly one launched from a location surrounded by an adversary, a military strike, particularly by air, aimed to eliminate something specified but avoiding wider harm, such as killing only the enemy commander. It was used by several nations in various wars. Sudden attacks were often used as a diversion while more serious actions were taken behind the scenes. For example, during the American Civil War, U.S. President Abraham Lincoln ordered an invasion of Virginia with the aim of ending slavery there, but told his generals not to take any risks and to return home if things went wrong. In modern warfare, military attacks are usually declared in advance by issuing a statement through a news agency or on the Internet. The attacker can be a country, a group of countries, or a private person or entity. A military attack can also be defined as a hostile action directed against another state or nation undertaken by the use of armed force. There are two types of military attacks: active and passive. An active military attack involves the use of armed forces in battle, while a passive military attack does not. For example, the United States has conducted military operations in other countries' territories without entering into direct conflict; these are called passive military attacks.