Air attacks on Normandy's coastal defences began in earnest on 5 June at 23:30, with RAF Bomber Command units targeting the primary coastal defences. The attack continued until 05:15, with of bombs dropped by 1,136 sorties; this marked the largest attack by Bomber Command in terms of tonnage up to that point in the war. Initial attacks on the Atlantic Wall proved ineffective, with poor weather and visibility making it difficult to accurately hit the bunkers and turrets. The bombing left the defences on Omaha, Gold and Juno virtually intact, yet did not damage Allied landing craft in the Channel (as many planners had feared it would). The Royal Canadian Air Force (RCAF) sent 230 bombers to bomb targets on Juno during this raid, yet damage was limited.