When at full strength an infantry regiment normally comprised two field battalions of about 800 men each or 8 - 10 in European armies during the nineteenth century , the regimental system underwent modification .
When at full strength an infantry regiment normally comprised two field battalions of about 800 men each or 8 - 10 companies . 
 With the widespread adoption of conscription in European armies during the nineteenth century , the regimental system underwent modification .