Texas Local Government Code - LOC GOV'T § 143.028. Eligibility for Promotion

(a) Except as provided by Sections 143.013 and 143.102, a fire fighter is not eligible for promotion unless the person has served in that fire department in the next lower position or other positions specified by the commission for at least two years at any time before the date the promotional examination is held. A fire fighter is not eligible for promotion to the rank of captain or its equivalent unless the person has at least four years' actual service in that fire department.

(b) Except as provided by Sections 143.013 and 143.102, a police officer is not eligible for promotion unless the person has served in that police department in the next lower position or other positions specified by the commission for at least two years immediately before the date the promotional examination is held. A police officer is not eligible for promotion to the rank of captain or its equivalent unless the person has at least four years' actual service in that police department.

(c) If a person is recalled on active military duty for not more than 60 months, the two-year service requirements prescribed by Subsections (a) and (b) do not apply and the person is entitled to have time spent on active military duty considered as duty in the respective fire or police department.