'Detained I' was an Allied amphibious assault on Solta island off the Dalmatian coast of German-occupied Yugoslavia near Vis island (18 March 1944).

The British and US force comprised 43 officers and 450 men landed by three infantry landing craft supported by guns embarked on three LCAs, and the force was otherwise escorted and supported by six motor gun boats. The flotilla of 12 vessels departed Komiza during the evening of 17 March, and during the early morning the men and their equipment were landed in the Tatinja inlet so that by dawn all was ready for the assault on the fortified garrison in Grohota.

At 06.00 the Allies opened fire with all their weapons on the housing occupied by the Germans, who were then invited to surrender. Men of a company of the 1/892^nd Regiment of Generalleutnant Albin Nake’s 264^th Division, the Germans refused and resisted for 30 minutes until 36 Allied ground-attack aircraft arrived and bombed the village. After this the Germans soon succumbed. The Allies suffered two men killed and 15 wounded, mostly to the effects of bombs from their own aircraft, and the Germans suffered six men killed, and 105 captured, most of the latter in wounded condition. The air attack cost the villagers of Grohota two persons killed and four injured.

Under the protection of Allied warplanes, the Allied troops re-embarked with their prisoners during the evening and returned to Vis.

At much the same time another convoy of three submarine chasers and three motor sailers departed left Vis island for Tatinja on Solta to evacuate any civilian refugees who wished to leave the island before Germans returned. Because not all the potential refugees were ready, the convoy was able to embark only about 250 people, although an Allied landing ship lifted another 130. The convoy returned to Vis at 01.45 on 20 March.

The German reaction to 'Detained I' was slow, and after few aerial reconnaissance sorties the Germans sent a party of 20 men during the night of 20/21 March, but this was evacuated before the break of day. Another landing was made during the night of 21/22 March, when four assault boats delivered two companies of the 264^th Division, but after 40 minutes decided to turn back to Split because five assault boats carrying a company of the Küstenjägerabteilung 'Brandenburg' of Generalmajor Alexander von Pfuhlstein’s Division 'Brandenburg' became lost at sea and sailed into Trogir. Finally, on the night of 22/23 March, all three companies arrived and started to fortify positions in Grohota.

'Detained I' revealed to each side the basic vulnerability of the German island garrisons, and few days later the Allies launched 'Endowment' against Hvar island with similar results. German fortification efforts then put a different complexion on matters, and when the partisans of he 26^th 'Dalmatia' Division launched a raid on Solta they could not eliminate fortified garrison before German reinforcements arrived from the mainland. After the raid the Luftwaffe, which until that time made only reconnaissance flights over Vis island, begun regular nocturnal bombing attacks that forced the Allies to move their troops to hills around Komiza harbour.