[6] On 19 February, two destroyers were sent in to probe the straits and the first shot was fired from Kumkale by the 240 mm (9.4 in) Krupp guns of the Orhaniye Tepe battery at 07:58.

Demolition parties of Royal Marines raided the Sedd el Bahr and Kum Kale forts, meeting little opposition.

The minesweepers, commanded by the chief of staff, Roger Keyes, were un-armoured trawlers manned by their civilian crews, who were unwilling to work while under fire.

The strong current in the straits further hampered minesweeping and strengthened Ottoman resolve which had wavered at the start of the offensive; on 4 March, twenty-three marines were killed raiding the outer defences.

A gunnery officer noted in his diary that de Robeck had already expressed misgivings about silencing the Ottoman guns by naval bombardment and that this view was widely held on board the ship.