It is my (wholly unsubstantiated) guess that the majority of Soviet personnel in Vietnam are in fact not Russian.
( It ( ( is ( ( my ( ( -LRB- ( ( wholly unsubstantiated ) -RRB- ) ) guess ) ) ( that ( ( ( the majority ) ( of ( ( Soviet personnel ) ( in Vietnam ) ) ) ) ( ( are ( in fact ) ) ( not Russian ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (NP (NP (PRP$ my) (PRN (-LRB- -LRB-) (ADJP (RB wholly) (JJ unsubstantiated)) (-RRB- -RRB-)) (NN guess)) (SBAR (IN that) (S (NP (NP (DT the) (NN majority)) (PP (IN of) (NP (NP (JJ Soviet) (NNS personnel)) (PP (IN in) (NP (NNP Vietnam)))))) (VP (VBP are) (ADVP (IN in) (NN fact)) (ADJP (RB not) (JJ Russian))))))) (. .)))
It is likely that most of them are from other places
( It ( ( is likely ) ( that ( ( most ( of them ) ) ( are ( from ( other places ) ) ) ) ) ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (ADJP (JJ likely)) (SBAR (IN that) (S (NP (NP (JJS most)) (PP (IN of) (NP (PRP them)))) (VP (VBP are) (PP (IN from) (NP (JJ other) (NNS places)))))))))