The chief of police shall be the chief of the acting police and all assistant police officers shall be in subordination to him and subject to his orders, except in cases otherwise provided by ordinance. It shall be his duty to cause the public peace to be preserved and see that all laws and ordinances are enforced within the city limits, and when any violation thereof shall come to his knowledge or be reported to him, he shall cause the requisite complaint to be made and see that all possible evidence is procured for the successful prosecution of offenders. (1990 Code)