Er...historical infinitives. I get what they do, they act as an indicative with the nominative as the subject, but translation proves a bit tricky. A&G says they should be translated as imperfect indicatives, but then goes on to translate 'ibi resistere ac propulsi' as 'there they would stand and fight.' And it also translates 'pars cedere' as 'a part gives way." Hello, present tense.
Clarification would be much appreciated.