When describing what was possible in a particular situation in the past, the phrase "insofar as was then possible" is commonly used. To provide some variation, some synonyms for this phrase include "to the extent that was feasible", "as far as was attainable at the time", and "within the limits of what could be done". Other options to convey a similar meaning include "within the parameters of the circumstances", "as much as was permitted", and "within the scope of available resources". Using varied language can help to make your writing more interesting and engaging for the reader.