Though it was ultimately redeemed by the Allied capture of Rome, and though it achieved complete tactical surprise, the Allied landing in January 1944 at Anzio failed to achieve the operational objective for which it was intended. Part of the reason is that the Germans had expected to be surprised in just such a way—and had plans ready.
"The Allied Landing at Anzio-Nettuno, 22 January–4 March 1944: Operation SHINGLE,"
Naval War College Review: Vol. 67:
4, Article 8.
Available at: https://digital-commons.usnwc.edu/nwc-review/vol67/iss4/8