The English Longbow:  this is the weapon that changed the face of medieval combat.  You are looking at a bow that was around 5-6 feet long.  Could fire different types of ammunition and when used by an expert was deadly at long distance.  When used en mass:  it could blot out the sky and devastate a cavalry charge.

longbow

 

History:

The bow, as a weapon, has been a round for over 10,000 years.   The term longbow has been found in documents from around 1500 and the English and Welsh were known for the deadly accuracy of their longbowman.  It has been hypothesized that due to the size of the bow and the draw strength that the English practiced bending the bow instead of drawing the bow.  In other words, they would hold the right hand (the one that held the arrow) and push their body into the bow.  With a draw strength ranging between 100-185 lbs, this was probably the only options for most people when using the bow.

Arrows:

Picture from Wikipedia

Due to the size of the bow, their were lots of different arrows that could be used – a larger bow had the ability to send a projectile with an over-sized head through the air.
Most of the military style arrows were carried in sheafs of 24 arrows.  One thing that these arrows had in common was the length.  They all measured at about 30 inches long.  But you would also have specialty arrow heads that the archer had access to:

Flight arrows were used for long range attacks – smaller heads equaled less weight to drag the arrow down after it was launched.

You also had the broadhead.  This arrow head had flared protrusions on the side of the head that would add weight to the arrow and bring it down at a faster rate when fired at the oncoming army.  This extra weight would allow the arrow to punch through the armor and into the flesh beneath it.

Along with these two main types you had piercing arrow heads, you also had blunt heads that would incapacitate while not necessarily killing the target.

Military Use:

Archers were used in medieval combat for centuries.   Archers were used to soften up infantry for decades until it was suggested that they might be good when used against cavalry.  The cavalry charged the infantry line and the archers fired over the heads of the infantry into the cavalry.  At some point, when the longbow and the broadhead arrow were put together, the arrow had enough velocity when it descended toward its target that it popped through the heavy armor that the cavalry wore and certainly was devastating on the horses that carried the knights into battle.  Up until this point, no army, without a cavalry, had won on the battlefield.  All of sudden the tides shifted (see the Battle of Agincourt).  No longer could you simple send a cavalry charge at the infantry or overwhelm with the greater cavalry.  After this point, lining up and fighting was not really an option anymore.  The English longbow changed the face of combat and changed the tactics that had to be used.