The hole commonly seen in some Chinese war swords, particularly in the blade near the guard, has both functional and symbolic purposes. This feature is known as a "blood groove," "fuller," or "bo hi." Here are a few reasons for its inclusion:

1. Weight Reduction: One of the primary purposes of the hole is to reduce the weight of the sword without sacrificing structural integrity. By removing material from the blade, the overall weight is reduced, allowing for greater maneuverability and ease of handling.
2. Flexibility and Balance: The blood groove also contributes to the flexibility and balance of the sword. It helps redistribute the weight along the blade, making it more responsive and agile during strikes and defensive maneuvers.
3. Blood Dispersion: Historically, it was believed that the blood groove helped disperse blood from the blade when it was withdrawn from a target, particularly in combat situations. This was thought to minimize suction and make it easier to remove the sword from an opponent's body. However, the actual effectiveness of blood grooves in this regard is a topic of debate among experts.
4. Symbolic and Aesthetic Considerations: The presence of a blood groove in Chinese war swords also has symbolic and aesthetic significance. It is a traditional design element that adds character and visual interest to the weapon, often enhancing its overall appearance.

It's important to note that the specific design and purpose of the blood groove may vary across different sword types, regions, and historical periods. The inclusion of a blood groove in a Chinese war sword is not unique to Chinese swords and can be found in various cultures' blades as well.