Weapons in WWI included tube artillery like guns, mortars, and howitzers. Machine guns allowed for rapid fire but were initially ineffective. Tanks were first developed by the British and deployed by several nations, though early models had issues with heat and reliability. Aircraft conducted reconnaissance and bombing but had high casualty rates. Chemical weapons like chlorine, mustard, and phosgene gases caused over 100,000 deaths, despite countermeasures like gas masks. Submarines threatened naval forces until sonar and hydrophones were developed for anti-submarine detection.