What is the main purpose of the M67 grenade?

The M67 grenade is designed primarily to inflict personnel casualties and damage to light equipment. This makes it an effective tool in combat situations, particularly in close-quarters engagements where it can be thrown at enemy forces to create lethal effects. Its fragmentation design allows it to disperse shrapnel over a wide area, significantly increasing the likelihood of injuring or incapacitating multiple personnel within its blast radius.

In contrast, the other answers focus on functions that the M67 grenade does not serve. For instance, it is not designed for signal communication, anti-armor engagements, or smoke obscuration. Each of these functionalities serves specific tactical purposes, but they do not align with the intended use of the M67 grenade, which is concentrated on direct combat effectiveness against enemy personnel and light material.