Complex sentence: The ships initially carried a pole mast above the conning tower, though shortly after commissioning, both ships had lattice masts added aft, and in 1910, the forward masts were also replaced with lattice masts.
Split into simpler sentences: The ships initially carried a pole mast above the conning tower, though shortly after commissioning, both ships had lattice masts added aft. In 1910, the forward masts were also replaced with lattice masts.