Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
fortify [ˈfɔːtɪfaɪ] vt (city) укрепля́ть (укрепи́ть*perf) (person) придава́ть*(прида́ть*perf) си́лы +dat
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: