Because factories was the first time a establishment had been made that allowed people to labor inside, instead of outside in the unpredictable weather. This fact plus many others opened doors to modern day labor or work employment, which changed history.
Their general performance early war was poor, due to them not being a real army, but rather more like quickly formed militia, consisting of untrained personnel. In all early battles there were outnumbered, and had little to no time to organize effective battle units. It was General Washington that managed to organize the militias into a regular army.
Corroborating sources allows a historian to increase the reliability of the information at hand. Having multiple sources in agreement makes it less likely for discrepancy
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