Source analysis is a skill so you should practice lots of it and get it marked by your teacher.
Some things to take note of:
- just because the source takes on a certain nationality, it does not mean the source is biased. You can only say if it is biased if the evidence in the source suggests so.
- just because the source is biased, it does not mean the reliability is lowered. In most cases, I would say that yes, a biased perspective does not present a factually accurate account however sometimes the bias is also reliable for providing the perspectives of soldiers at the time
- just because the source is a primary source, it does not necessarily make it reliable - while it is a first hand account, you must also consider if there is bias, emotive language, is it from an official source? If so, was it subject to censorship? You should take note of official sources because censorship was prevalent during this period, and they often romanticised soldier life and hid images of dirty trenches from the public.
- always talk about corroboration of sources I.e can the factual information in your source be backed up by other sources?
- for trench warfare in particular you need to know your content as this will help you for the usefulness section. Compare your knowledge of the dot point and the information provided in the source, and see if the source supports your knowledge, and then SPECIFY it. i.e this source is useful for showing that the soldiers indeed suffered gangrene, lice, freezing temperatures etc.
Good luck!!! I remember my first assessment on source analysis and I accidentally called the Daily Mail a reputable source and lost marks for it ahahaha