A few weeks after this event a call was made for additional surgeons for the army then serving in the Crimea, and young Flower, partly, perhaps, from patriotic motives, and partly with a view of extending his practical experience in surgery, promptly volunteered his services, which were accepted. After spending a few idle months with the Depôt Battalion then stationed at Templemore, in Ireland, he was gazetted as Assistant-Surgeon to the 63rd (now the First Battalion of the Manchester) Regiment; and in July 1854 embarked with his regiment at Cork for Constantinople. On its arrival in the east the regiment was at once hurried up to join the main army at Varna, whence it proceeded to take part in the expedition to the Crimea, where both officers and men suffered severely from exposure to the inclemencies of the climate and an insufficient commissariat during the early months of the campaign. For ten weeks together, it is reported, neither officers or men took off their clothes, either by night or by day, and for the first three weeks all ranks were compelled to get such sleep as they could obtain on the bare ground. Flower, who was present at the battles of the Alma, of Inkerman, and of Balaclava, as well as at the fall of Sebastopol, underwent many and thrilling experiences during the campaign, alike in the field and in the hospital. The hardships and privations which caused the strength of his regiment to be reduced by nearly one-half within the short period of four months, could not but tell severely on the constitution of the young surgeon, which was never very robust; and from some of the effects of these he suffered throughout his life. Nevertheless, in spite of all this, in the intervals of duty, Flower, with but scant materials at his disposal, managed to find time and energy sufficient to make a considerable number of vivid pen-and-ink, or dashes of ink-and-water, sketches of his surroundings, including one of his own tent overturned by the terrible snow-storm of 14th November 1854, and a second of the wrecked condition of the camp in general at the end of the tempest. A panoramic view of Constantinople and a sketch of the military hospital at Scutari were also among his artistic productions at this period. In recognition of his services, Flower, after being invalided home, received from the hands of Her Majesty, Queen Victoria, the Crimean medal, with clasps for the Alma, Inkerman, Balaclava, and Sebastopol; while he was also permitted to accept from H.M., the Sultan, the Turkish war-medal.