Split flags and swallowtail flags

Why do flags in Scandinavia have come in two shapes, depending on whether they are state flags or not, while in many other countries all flags are rectangular? Is this difference a Danish invention? What was the original meaning of this difference?

How did these two shape diverge? Does the difference signify a pennant included in one shape but not in the other? Was it wear and tear of the fly end of a rectangular flag or of the tips of a forked flag?
Peter Hans van den Muijzenberg, 25 February 2008

This is one way to make one basic design fit two different uses. Other countries put a shield on the state flag, which is another way. The practice of using splits is not exclusively Scandinavian though, but also Baltic, with Poland, Estonia and Germany currently using such flags for some purposes. Does there have to be a meaning, apart from the function of distinguishing different uses and status? We should be careful about reading symbolism into everything.

It might well have been a Scandinavian invention, at least Sweden adopted the practice too. Through Danish tradition the tails went on to Iceland (and the 1814 flag of Norway) and through Sweden to Norway and Finland. The Danish participation in the struggle for dominance in the Baltic may also have influenced other states in the neighborhood.
Jan Oskar Engene, 25 February 2008

The two shapes diverged according to the Danish regulations of 1625, when the swallow-tailed ensign was reserved for the battle fleet and the square-ended flag relegated (or restricted if you prefer) to the merchant marine (which is one way of doing it, and rather better than some). This formally established the principle adhered to ever since, but I imagine that it was simply confirmation of an existing practice? Whether that practice had a particularly Scandinavian heraldic basis or was just a local tradition I really have no idea?
Christopher Southworth, 25 February 2008

Perhaps the reason (and also the reason so many battle guidons are either swallow-tailed or pennon-shaped) is simply that they take less cloth to make (and are therefore lighter) and have pointed ends (which therefore fly more freely), and as such were a more practical shape for flying from horseback. Since both battle flags and postal flags would originally have been flown from horseback, they might be more likely to be this shape than rectangular.

It would be interesting to compare the shapes of flags from countries that were primarily army powers tot hose that were primarily navy powers, to see whether the incidence of swallow-tailed (horseback) vs. rectangular (shipboard) military flags is different for these two groups of countries.
James Dignan, 25 February 2008

From what evidence we have it would appear that many pre-heraldic European gonfanons (such as the Oriflamme of France or many Papal Pallia) were triple- or multi-tailed, and were possibly developed from the Roman flammula and its later post-Roman equivalents? In English medieval practice, however, a knight pennoncier flew a forked-tailed pennant from his lance, and if he was promoted to a knight banneret his lance pennant became square-ended.

To the best of my knowledge in English practice banners of arms were almost invariably squared, whilst heraldic standards always narrowed between hoist and fly and were usually finished with double-descate or descate tails, however, during the medieval period there were a huge number of different terms for flags which were differently applied on different occasions.
Christopher Southworth, 26 February 2008