A month later , the battle on the peninsula had bogged down .
The success of the German submarine U-21 in sinking two British predreadnoughts forced Ark Royal to move to a safer anchorage at Imbros at the end of May .
A month later , the battle on the peninsula had bogged down and the success of the German submarine U-21 in sinking two British predreadnoughts forced Ark Royal to move to a safer anchorage at Imbros at the end of May .