The crime of assault varies from state to state (and under federal law), but is generally defined as intentionally putting another person in reasonable apprehension or fear of an imminent (immediate) harmful or offensive contact. The crime of assault may be committed even if there is no physical contact, as the criminal physical contact constitutes the separate crime of battery.

The crime of assault with a deadly weapon (also known as aggravated assault) occurs when someone uses a deadly weapon (gun, knife, club, tire iron, brass knuckles, etc.) during an assault.

In Montana (MT), assault is defined under Montana Code Annotated (MCA) 45-5-201. The law states that a person commits the offense of assault if they purposely or knowingly cause bodily injury to another, purposely or knowingly cause reasonable apprehension of bodily injury in another, or negligently cause bodily injury to another with a weapon. Aggravated assault, or assault with a deadly weapon, is a more serious offense and is covered under MCA 45-5-202. This occurs when a person causes serious bodily injury to another or uses a weapon to cause reasonable apprehension of serious bodily injury. The use of a deadly weapon elevates the crime to aggravated assault due to the increased potential for significant harm. The definition of a deadly weapon includes, but is not limited to, guns, knives, clubs, and other items that could be used to inflict serious injury or death. The penalties for assault and aggravated assault in Montana vary based on the severity of the offense and can include fines, imprisonment, or both.