1st Division had made the initial landing at Anzio alongside US troops in Operation Shingle on 21 January. Its 90th LAA Rgt landed a SP Bofors battery with the first wave and the whole regiment was ashore by D + 5 to defend the field artillery positions. At first all went well, but the commander of the operation waited too long to build up his forces and lost the initiative. The Germans quickly contained the beachhead and by 1 February were driving the Allied troops back towards the sea, and sending over waves of air attacks. 168 LAA Battery from 56th (East Lancashire) LAA Rgt landed on 5 February, and the first of 100th LAA Rgt's arrived on 14 February as 56th (L) Division arrived in the beachhead. The five LAA batteries, coordinated by the commanding officer (CO) of 90th LAA Rgt, had to cover the spread of six British field artillery regiments, which were unable to disperse or find cover in the congested beachhead.