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))))))) (. .)))
All of the personal in Vietnam are from Russian
( ( All ( of ( ( the personal ) ( in Vietnam ) ) ) ) ( are ( from Russian ) ) )
(ROOT (S (NP (NP (DT All)) (PP (IN of) (NP (NP (DT the) (JJ personal)) (PP (IN in) (NP (NNP Vietnam)))))) (VP (VBP are) (PP (IN from) (NP (NNP Russian))))))