Complex sentence: Frontinus had a distinguished military career, and he draws on his own experience as a general in Germany under Domitian, but similarities between the anecdotes he records and versions in other Roman authors like Valerius Maximus and Livy suggest that he drew mainly on literary sources.
Split into simpler sentences: Frontinus had a distinguished military career, and he draws on his own experience as a general in Germany under Domitian. However, similarities between the anecdotes he records and versions in other Roman authors like Valerius Maximus and Livy suggest that he drew mainly on literary sources.