In the legal system of the United States and elsewhere, assault and battery charges are generally issued and prosecuted as a single offense. Historically, however, assault and battery are two distinct concepts. An assault is variously understood as the attempt or the apprehended imminence of an act of physical violence or some other form of unwanted physical contact, and a battery as the application of physical force toward an end of bodily harm or some other form of offense.
In cases in which assault and battery charges can be filed with some reasonable expectation of success, it will be in the circumstances that it can be shown that an intent to cause physical violence or offense was first apprehended by the victim and then experienced in its effects.
It is not unusual for assault charges to be filed without being accompanied by charges of battery, in instances in which the promised action did not occur with any physical contact. It is rarer but still legally conceivable for battery charges to be filed without any corresponding assault charges, as when the application of physical force is performed without the affected individual having any awareness of it. One unusual form of battery which has been identified as occurring in legal practice can take place in the course of a surgical operation which performs some action on the patient's body which had not been previously agreed to.
The understanding of assault charges on the books in various jurisdictions of the United States commonly see assaults as attempts at battery, which if pursued without any charges of battery, can be said to have been failed attempts at battery. An example of this commonly furnished by legal scholars is that of a punch being directed at a person without connecting.
An assault may also be found to have been committed against an individual in cases where he or she was not specifically the object of the malicious intent on the part of the actor of the assault. Some application of force which was directed against a specific person but had the capability to harm bystanders could be considered to represent an assault against the bystanders.
One central but sometimes vaguely defined component of understandings of assault can be found in the form of the requirement that a degree of immediacy be involved in the apprehension of danger. In this way, the threat that was being directed at the individual and may have been fulfilled with a battery can be considered "imminent." The actor of an assault charging at another person might be considered the most clear-cut example of this immediacy principle.
In contrast, a long-term threat made to a person, in which both actor and recipient recognize as falling within that time frame, would not be considered an assault. In some cases, the principle of immediacy has been given greater latitude for interpretation. English legislative proceedings established that telephone calls perceived as threatening might lead to assault charges if the threat was felt to be very immediate.