The concept of a "blood groove," more accurately known as a fuller or a groove, on a sword is often misunderstood. A fuller is a groove that runs along the length of a blade, typically on both sides, without extending into the cutting edge. Its primary purpose is to reduce weight and improve the balance of the sword.

Contrary to popular belief, a fuller does not significantly weaken a sword. In fact, it can enhance the structural integrity of the blade. The removal of excess material through the fuller reduces the weight without compromising the overall strength of the sword.

The misconception that a fuller strengthens a sword may stem from the mistaken notion that it acts as a channel for blood to flow out, hence the term "blood groove." However, historical evidence suggests that the primary purpose of a fuller was weight reduction, improved balance, and increased flexibility.

The presence of a fuller in a sword also affects its cutting properties. By redistributing the weight along the blade, it can enhance the sword's agility and maneuverability, allowing for faster and more precise cuts.

It's worth noting that the depth and width of a fuller can vary depending on the sword's design, era, and intended purpose. While fullers are commonly found in many historical and modern swords, not all swords have them. Their presence or absence does not determine the overall quality or effectiveness of a sword.

In summary, a fuller, also known as a groove or blood groove, on a sword does not weaken the blade. It is primarily designed to reduce weight, improve balance, and enhance the cutting properties of the sword. The structural integrity of a sword is influenced by various factors beyond the presence or absence of a fuller, including the quality of the materials used and the craftsmanship of the swordsmith.