jmc

We first think of the German delegates forming a single German block, denoted G, the French delegates forming a single French block F, and the Italian delegates forming a single Italian block I. Then there are $3!=6$ ways to arrange the three blocks in a row: $$\text{FGI, FIG, GFI, GIF, IFG, IGF.}$$ Within each block, there are $6!$ ways to arrange the German delegates, $5!$ ways to arrange the French delegates, and $3!$ ways to arrange the Italian delegates. Therefore, there are $$3!\times 6!\times 5!\times 3!=6\times 720\times 120\times 6=\boxed{3,110,400}$$ ways to seat all 14 delegates.