Havmanden-class submarines
... that plans for the Royal Danish Navy's 1911 Havmanden-class submarines were seized by the Austro-Hungarian Navy during the First World War and used as the basis for their own U-20-class submarines?
... that plans for the <a href="./Royal_Danish_Navy" id="mwF0w" rel="mw:WikiLink" title="Royal Danish Navy">Royal Danish Navy</a>'s 1911 <b id="mwF00"><a class="mw-redirect" href="./Havmanden_class_submarine_(1911)" id="mwF04" rel="mw:WikiLink" title="Havmanden class submarine (1911)"><i id="mwF08">Havmanden</i>-class submarines</a></b> <i id="mwF1A">(pictured)</i> were seized by the <a href="./Austro-Hungarian_Navy" id="mwF1E" rel="mw:WikiLink" title="Austro-Hungarian Navy">Austro-Hungarian Navy</a> during the <a href="./World_War_I" id="mwF1I" rel="mw:WikiLink" title="World War I">First World War</a> and used as the basis for their own <a about="#mwt28" data-mw='{"parts":[{"template":{"target":{"wt":"sclass","href":"./Template:Sclass"},"params":{"1":{"wt":"U-20"},"2":{"wt":"submarine"},"3":{"wt":"1"}},"i":0}},"s"]}' href="./U-20-class_submarine" id="mwF1M" rel="mw:WikiLink" title="U-20-class submarine" typeof="mw:Transclusion"><i>U-20</i>-class submarines</a>?