Answer:
In order to tell whether the evidence in the journal is valid, I would try to corroborate the events detailed in the journal with other sources like newspapers, military records, etc. I would read the journal entries for clues depending on the research question I was seeking to answer.
Explanation:
The process of interpreting a battlefield journal would entail reading the passages in the journal and separating the different statements made into categories like dates and facts, and emotions, and opinions expressed on the part of the soldier. I imagine that if I am reading a battlefield journal of an individual soldier as part of my research, then my research question is probably in regards to his emotions and how he deals with the trauma of being on the battlefield. But if I am concerned with whether the events described are factual, I would try to corroborate it by reading other journals of other soldiers if possible and checking events and details against the military and personal records that are available for the soldier.