U-15 was constructed at AG Weser in Bremen for the Austro-Hungarian Navy and then shipped by rail in sections to Pola, where the sections were riveted together. Though there is no specific mention of how long it took for U-15's sections to be assembled, a sister boat, the German Type UB I submarine UB-3, shipped to Pola from Germany in mid-April 1915, was assembled in about two weeks.[6][Note 1] U-15 was launched in April.