WASHINGTON (AP) – The Pentagon is lifting its ban on women serving in combat, opening hundreds of thousands of front-line positions and potentially elite commando jobs after generations of limits on their service, defense officials said Wednesday.

The changes, set to be announced Thursday by Defense Secretary Leon Panetta, will not happen overnight. The services must now develop plans for allowing women to seek the combat positions, a senior military official said. Some jobs may open as soon as this year, while assessments for others, such as special operations forces, including Navy SEALS and the Army’s Delta Force, may take longer. The services will have until January 2016 to make a case to that some positions should remain closed to women.

The groundbreaking move recommended by the Joint Chiefs of Staff overturns a 1994 rule prohibiting women from being assigned to smaller ground combat units.