Yes, the rifle bayonet is a descendant of the pike. Essentially, the pike protected the musketeers from the saber- and pistol-armed horse-mounted cavalry (you'd think someone would have done it with archers, but I can't recall any examples). Lots of history here. It is hard to keep infantrymen of centuries ago from running away from a horse cav charge. Quite an impressive sight, I think--the charge of horse cav, I mean. Without pikes to keep the cavalry from running down the infantry and killing them without any risk to the riders, infantry couldn't hold. With pikes--and then plug bayonets, then ring bayonets of varies forms--infantry could hold against cavalry in open terrain. Prior to the tactical innovation of mixing pikes with guns, horse cav dominated open terrain. With pikes mixed in, infantry could hold (though often didn't due to lack of training or lack of discipline). An important tactical innovation.
However, the bayonets we see today are not designed to stop horse cavalry. They are more related to WWI where close-range infantry charges (somewhat like Picket's Charge at Gettysburg) and rifles with small magazine capacities (typically five to eight rounds) were common. The bayonet was useful in that situation because of the very short distances--a couple of feet--and the lack of ammunition. In my personal opinion as an infantryman, it's always better to shoot the other guy than to try to stab him.
Because of the (diluted) influence of our WWI experiences, the bayonet is maintained in the arsenal for a couple of reasons. Crowd control. A rifle with a bayonet can push people back, often without lethally wounding anyone. The second reason is more difficult to explain except as an aspect of discipline. A steady line of infantry with fixed bayonets can create a moral advantage in the appropriate situation.
I suspect the major reason for issuing a bayonet that can actually be used as a knife (the one for my M16 was way too soft) is because of weight and utility. Everyone is going to carry a knife anyway. Some of us carried multiple knives (I carried three) plus a bayonet. I can reduce that by one if my bayonet can be used as a knife, making my load that much less heavy.
However, the bayonets we see today are not designed to stop horse cavalry. They are more related to WWI where close-range infantry charges (somewhat like Picket's Charge at Gettysburg) and rifles with small magazine capacities (typically five to eight rounds) were common. The bayonet was useful in that situation because of the very short distances--a couple of feet--and the lack of ammunition. In my personal opinion as an infantryman, it's always better to shoot the other guy than to try to stab him.
Because of the (diluted) influence of our WWI experiences, the bayonet is maintained in the arsenal for a couple of reasons. Crowd control. A rifle with a bayonet can push people back, often without lethally wounding anyone. The second reason is more difficult to explain except as an aspect of discipline. A steady line of infantry with fixed bayonets can create a moral advantage in the appropriate situation.
I suspect the major reason for issuing a bayonet that can actually be used as a knife (the one for my M16 was way too soft) is because of weight and utility. Everyone is going to carry a knife anyway. Some of us carried multiple knives (I carried three) plus a bayonet. I can reduce that by one if my bayonet can be used as a knife, making my load that much less heavy.