Complex sentence: The mainstay of the DAF, the P-40 Tomahawk and Kittyhawk was originally the DAF's only adequate air superiority fighter, soon also modified to become a highly successful ground attack aircraft.
Split into simpler sentences: The mainstay of the DAF, the P-40 Tomahawk and Kittyhawk was originally the DAF's only adequate air superiority fighter. It was also quickly modified to become a highly successful ground attack aircraft.