Complex sentence: U- 1051 was forced to the surface by the use of depth charges, then a gun battle ensued with U- 1051 finally sinking after it had been rammed by HMS "Aylmer".
Split into simpler sentences: U- 1051 was forced to the surface by the use of depth charges. A gun battle then ensued, with U- 1051 finally sinking after it had been rammed by HMS "Aylmer".