Invasion...

A serial killer is traditionally defined as a person who has murdered two or more people over a period of more than a month, with down time (a "cooling off period") between the murders. The motivation for killing is usually based on psychological gratification. Some sources, such as the FBI, disregard the "three or more" criteria and define the term as "a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone" or, including the vital characteristics, a minimum of two murders. Most of the killings involve sexual contact with the victim, but the FBI states that motives for serial murder include "anger, thrill, financial gain, and attention seeking". The murders may have been attempted or completed in a similar fashion and the victims may have had something in common; for example, occupation, race, appearance, sex, or age group.

Assassins can be traced back to just before the First Crusade, around 1080. There has been much difficulty finding out much information about the origins of the Assassins because most early sources are either written by enemies of the order or based on legends, or both. Most sources dealing with the order's inner working were destroyed with the capture of Alamut, the Assassins' headquarters, by the Mongols in 1256. However, it is possible to trace the beginnings of the cult back to its first Grandmaster, Hassan-i Sabbah.

Reconnaissance is the military term for exploring beyond the area occupied by friendly forces to gain vital information about enemy forces or features of the environment for later analysis and/or dissemination.
Often referred to as recce (British and Canadian English) or recon (American English, Australian English), the associated verb is reconnoitre in British and Canadian English or reconnoiter in American English.
Examples of reconnaissance include patrolling by troops (LRRPs, Rangers, scouts, or military intelligence specialists), ships or submarines, manned/unmanned aircraft, satellites, or by setting up covert observation posts. Espionage normally is not reconnaissance, because reconnaissance is a military force's operating ahead of its main forces; spies are non-combatants operating behind enemy lines.

The Department of Defense (Defense Department, USDOD, DOD, DoD or the Pentagon) is the executive department of the government of the United States charged with coordinating and supervising all agencies and functions of the government concerned directly with national security and the United States Armed Forces. The Department is also the largest employer in the world, with more than 2.13 million active duty soldiers, sailors, marines, airmen, and civilian workers, and over 1.1 million National Guardsmen and members of the Army, Navy, Air Force, and Marine Reserves. The grand total is just over 3.2 million servicemen, servicewomen, and civilians.
The Department – headed by the Secretary of Defense – has three subordinate military departments: the U.S. Department of the Army, the U.S. Department of the Navy, and the U.S. Department of the Air Force which oversee the U.S. Army, U.S. Navy, U.S. Marine Corps, and the U.S. Air Force. In addition, four national intelligence services are subordinate to DOD - the Defense Intelligence Agency (DIA), the National Security Agency (NSA), the National Geospatial-Intelligence Agency (NGA), and the National Reconnaissance Office (NRO). Other Defense Agencies include Defense Advanced Research Projects Agency (DARPA), the Defense Logistics Agency (DLA), the Missile Defense Agency (MDA), Defense Threat Reduction Agency (DTRA), and the Pentagon Force Protection Agency (PFPA), all of which are under the command of the Secretary of Defense. DOD's military operations are managed by nine regional or function Unified Combatant Commands. DOD also operates several joint services schools, including the National Defense University (NDU) and the National War College (NWC).
The Department is allocated the highest level of budgetary resources among all Federal agencies, and this amounts to more than one-half of the annual Federal discretionary budget.
On February 26, 2013 the Senate confirmed Chuck Hagel as Secretary of Defense, replacing the retiring Leon Panetta, after a pitched nomination battle and a narrow vote.