Perhaps you should try some spelling variations:
military acts » military art, military actions, military action
19th century » 18th century, 20th century
imf history » brief history
2f history » etf history, ref history, tnf history
2018 19th » 2018 15th, 2018 14th, 2018 9th

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: %((military acts) OR (military aspects)) AND science %((2f history) OR (imf history)) %2018 19th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((military acts) OR (military aspects)) and science %((2f history) or (imf history)) %2018 19th century%22".
• Adding a wildcard symbol may retrieve word variants: %((military acts) OR (military aspects)) and science %((2f history) or (imf history)) %2018 19th century%22*.