With tensions again on the rise between Prussia and Denmark by the end of the year, "Grille" was allocated as the flagship for Prince Adalbert, the commander of the Prussian fleet. Following the outbreak of war in February 1864, she was activated for this purpose on 10 March, by which time a pair of 12-pound guns had been fitted. "Grille" remained in port when Eduard von Jachmann took several vessels to sea to attack the Danish blockade, resulting in the Battle of Jasmund in March. Adalbert came aboard the vessel on 29 March at Stralsund, and on 6 April, he observed training exercises with the gunboats in the Bay of Greifswald. "Grille" sortied on 14 April with Adalbert aboard for a sweep Bay of Pomerania that resulted in an encounter with the Danish ship of the line and the steam frigate . "Grille" opened fire at long range, leading to an indecisive two-and-a-half-hour battle in which "Grille" easily outran the more powerful Danish vessels. She fled back to Swinemünde, where the gunboats of the 1st Flotilla and Jachmann's squadron covered her approach. As it was nearing dark, the Danish commander, Admiral Edvard van Dockum, chose to break off the pursuit.