'Hartherz' was a U-boat wolfpack operation in the Atlantic to locate and attack 'KMS' and 'MKS' convoys (4/7 February 1943).

The wolfpack was created in the area to the west of the Bay of Biscay with U-71, U-107, U-183, U-332, U-519, U-572, U-584, U-621, U-628, U-653 and U-753 to attack any 'KMS' and 'MKS' convoys located by the German navy’s B-Dienst radio intercept and decrypting service on the route to and from Gibraltar, but located no convoys. Kapitänleutnant Günter Eppen’s U-519 was lost in the Bay of Biscay to an unknown cause some time after 30 January, and U-628 was attacked in the Bay of Biscay by British aircraft on 3 February.