The Allies believed that attacking the waterfront town of Gallipoli and taking over it would take the stress of the western front and win them the war
The Allies launched an attack on the 2 forts blocking the entrance into Gallipoli. They thought their battleships could get them a path through and mean they could capture the base but they didn't know that there were mines in the sea which blew up a few ships and forced a retreat
They tried a different approach and attempted a land attack by sending soldiers onto beaches but due to bad information and old maps many of the beaches they landed on had large cliffs that they had to climb over and it made it easy for the turkish soldier's to rain down bullets into the soldier's.