Two-handed swords, such as the longsword, greatsword, or zweihänder, were developed and used for several reasons:

1. Increased Reach and Power: Two-handed swords allowed the wielder to extend their reach and deliver more powerful strikes. By utilizing both hands on the hilt, the wielder could generate greater force and leverage, resulting in more effective cuts, slashes, and thrusts.
2. Versatility: Two-handed swords provided versatility in combat. With a longer reach and increased control, the wielder could engage opponents at various distances and adjust their grip as needed. This flexibility allowed for a wider range of offensive and defensive techniques, making the sword suitable for both cutting and thrusting attacks.
3. Defensive Capabilities: The longer reach and two-handed grip of these swords offered improved defensive capabilities. The wielder could employ larger parries, blocks, and disarms, providing better protection against incoming attacks. The size and weight of two-handed swords also acted as a deterrent, creating a psychological advantage by intimidating opponents.
4. Adaptation to Armor: Two-handed swords were developed during a time when plate armor became prevalent on the battlefield. These swords were designed to penetrate or exploit the gaps in armor, utilizing the additional force generated by two hands to overcome the defensive capabilities of armored opponents.
5. Formation-based Warfare: Two-handed swords were used in formations and group combat, such as the pike and shot formations during the late medieval and Renaissance periods. These swords, with their longer reach, were effective in breaking enemy formations and countering opponents armed with polearms or shorter weapons.
6. Symbolism and Status: Two-handed swords were often associated with knights, nobility, and the elite warrior class. Wielding a large, two-handed sword became a symbol of prestige, power, and skill, signifying the status of the warrior.

It's important to note that the use of two-handed swords varied across different time periods and regions. While they were prominent during the late medieval and Renaissance periods in Europe, other cultures, such as the Japanese with their nodachi or ōdachi, also had their own variations of two-handed swords.

The specific development and popularity of two-handed swords were influenced by advancements in armor, changes in warfare tactics, cultural preferences, and the evolving needs of combat over time.