Complex sentence: The most effective portion of the force was the 3,000-strong special police, deployed in 12 battalions with a military structure; an additional 9,000--10,000 regionally-organized reserve police were grouped into 16 battalions and 10 independent companies.
Split into simpler sentences: The most effective part of the force was the 3,000-strong special police who deployed in 12 battalions and adopted a military structure. The reserve police were grouped into 16 battalions and 10 independent companies.