'Crawdad' was an Allied contingency plan, created as an alternative to 'Buffalo', 'Grasshopper' and 'Turtle', for Major General Lucian K. Truscott’s US VI Corps to break out of its 'Shingle' beach-head at Anzio, on the western coast of Italy, along the axis toward Ardea and Rome, in the event that Generaloberst Eberhard von Mackensen’s 14th Army of Generalfeldmarschall Albert Kesselring’s Heeresgruppe 'C' fell back more rapidly than expected after the advance of Lieutenant General Mark W. Clark’s US 5th Army from the line of the Rapido and Garigliano rivers toward Rome (March/April 1944).
On 5 May General the Hon. Sir Harold Alexander, heading the Allied Armies in Italy command, visited the headquarters of the VI Corps, where Truscott outlined for him the four alternate plans which the corps staff, at Clark’s direction, had developed during the two preceding months. These plans were 'Buffalo', 'Crawdad', 'Grasshopper' and 'Turtle'.
'Grasshopper' outlined an attack to the east in the direction of Littoria-Sezze with the object of making contact with the 5th Army’s main force advancing to the north-west from the Cassino area. Only if troops on the southern front appeared to be bogged down and in need of help to achieve a junction with the 'Shingle' lodgement was 'Grasshopper' to be mounted.
'Buffalo' corresponded most closely to the original strategic concepts embodied in 'Shingle' and 'Diadem', and called for a thrust to the north-east through Cisterna, Cori and Artena to Valmontone with the object of blocking Highway 6 and thereby cutting off the retreat of the right wing of Generaloberst Heinrich-Gottfried von Vietinghoff-Scheel’s 10th Army. The destruction of a significant part of the 10th Army would open the road to Rome along Highway 6.
'Turtle' called for an attack astride the Via Anziate (the road linking Anzio and Rome) and the Rome railway to the north through Carroceto and Campoleone to a junction with Highway 7 about 1 mile (1.6 km) to the south of Lake Albano in the Alban hills.
'Crawdad' outlined a drive through Ardea, 12 miles (19 km) to the northwest of Anzio and approximately paralleling the coast to the south-west of the Alban Hills. In terms of distance, 'Crawdad' offered the shortest route to Rome, but the road network was less favourable than that offered by Highway 7.
After assessing the four plans, Alexander quickly dismissed all but 'Buffalo'.