The word 保卫 is formed by combining two independent characters, each carrying a related core meaning, to create a new, unified concept. The first character, 保, fundamentally means "to protect" or "to keep safe", while the second, 卫, means "to guard" or "to defend". Their conceptual alignment allows them to merge seamlessly, with 保 emphasizing the act of preservation and 卫 adding the dimension of active defense against external threat, resulting in a compound whose combined meaning, "to defend and safeguard", is more comprehensive and active than either character alone.