In the late 1990s, these extremist groups suffered major defeats by Kurdish forces.
( ( In ( the ( late 1990s ) ) ) ( , ( ( these ( extremist groups ) ) ( ( ( suffered ( major defeats ) ) ( by ( Kurdish forces ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (DT the) (JJ late) (NNS 1990s))) (, ,) (NP (DT these) (NN extremist) (NNS groups)) (VP (VBD suffered) (NP (JJ major) (NNS defeats)) (PP (IN by) (NP (NNP Kurdish) (NNS forces)))) (. .)))
Kurdish forces believed they needed to stop all extremist groups.
( ( Kurdish forces ) ( ( believed ( they ( needed ( to ( stop ( all ( extremist groups ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Kurdish) (NNS forces)) (VP (VBD believed) (SBAR (S (NP (PRP they)) (VP (VBD needed) (S (VP (TO to) (VP (VB stop) (NP (DT all) (NN extremist) (NNS groups))))))))) (. .)))