For regular verbs, the imperfect tense is formed from the stem of the 2nd person pluralnous form of the present tense and one of the three possible endings:
For all verbs ending in -er
For regular -ir and -re verbs
For some irregular verbs, usually ending in -re and -ir
The past historic is only used in written French to describe a specific action which has been completed in the past. It is usually found in novels and historical writings. It is not essential to use the past historic when writing as the perfect tense (passé composé) can be used in its place. However, it is important to be able to recognize the past historic in order to understand a text in which it features.
Below is an example from a journal excerpt.
“John fut nommé consultant pour le projet et entreprit, avec Eckert et Mauchly la rédaction de la spécification de ce qui aurait pu être le premier ordinateur au monde. Ce travail prit la forme d’un document d’une dizaine de pages et d’une grande clarté…”