The historical present is less a verb tense in English and more a narrative technique. As most English speakers can explain, history necessarily involves the past. Speaking about historical events is naturally the stuff of the simple past tense, for example he ate, the past perfect, or he had eaten, the past progressive, as in was eating, or the perfect past progressive, that is had been eating. While that may be grammatically true, when a lecturer, storyteller, or other speaker who is relaying past events gets caught up in the narrative, it is very common to slip into what is termed the historical present.
Communicating pure information about the past is less likely to shift into the historical present. Stating that a battle took place on a particular date, for example, doesn’t tempt the speaker to elaborate, emotionally or psychologically identify, other otherwise become involved as anything more than the conveyor of a fact. When the speaker has some kind of personal commitment to the information, however, shifting into the historical present is far more likely.
If the subject is something the speaker has put many hours into researching, there’s a good likelihood that the story has come alive through mental images. If it is something that occurred to a friend or relative, or similar to such an event, the speaker is likely to feel an emotional connection that causes events that are over and done with to seem to be unfolding in the midst of the linguistic stream. Grammatically pulling the past into the present through use of the historic present reinvests it with new life, making it more palpable for the listener’s imagination.
Typically, the use of the historic present is bookended at both the message’s beginning and ending with the past. As the details gain weight or the narrative gains momentum, the speaker allows the present and the past to merge and overlap until the two seem identical. As the tale draws to a conclusion, the speaker begins to remember that the past is over and a story is being told and thus returns the remainder of the history to the past tense.
For example, a lecturer who is talking about a particularly gruesome Civil War battle might begin with a list of facts: when the battle occurred, how many soldiers were involved, and how many were killed. The lecturer may feel the students’ lack of involvement and want to drive home exactly how dismal the circumstances were. Facts and figures give way to an unfolding, present-tense narrative, for example, “A heavy fog begins to roll across the battlefield, and soon soldiers are fighting blind, completely unable to see anything or anyone who might be just a few feet away.” The students are likely to become more interested, which feeds the speaker’s impulse to remain in the present tense until the tale returns to the past — “by the time the battle was over, a thousand bodies sprawled across the ground” — and the story reaches its end.