Unlike the heavier guns, these smaller weapons are in widespread use due to their low cost and ability to quickly follow the target. Classic examples of autocannons and large caliber guns are the 40 mm autocannon and the 8.8 cm FlaK 18, 36 gun, both designed by Bofors of Sweden. Artillery weapons of this sort have for the most part been superseded by the effective surface-to-air missile systems that were introduced in the 1950s, although they were still retained by many nations. The development of surface-to-air missiles began in Nazi Germany during the late World War II with missiles such as the Wasserfall, though no working system was deployed before the war's end, and represented new attempts to increase effectiveness of the anti-aircraft systems faced with growing threat from [bomber]s. Land-based SAMs can be deployed from fixed installations or mobile launchers, either wheeled or tracked. The tracked vehicles are usually armoured vehicles specifically designed to carry SAMs.

Smaller weapons are able to be used because of their low cost as well as what other factor?