Weapons Technology involves further development of existing weapons systems. By providing more energy to the weapons and channeling that energy more efficiently, weapons systems become more powerful and do more damage.
Each level of Weapons Technology research increases the weapon strength of both ships and defenses by 10% of their base value. Weapons Technology should be upgraded as fleet size grows. Each upgrade also improves the strength of Interplanetary missiles. During combat, the Weapons Technology level of the attacker compared to the defender can alter the outcome of the battle.
When comparing the cost of upgrading Weapons Technology vs building more ships, remember that research cannot be destroyed while ships can.