I would look to the Vietnamization program of 1969 - 73. It worked pretty well and had no formal, public timeline for withdrawal. (There was a w/in govt timeline of ccourse, but it was not relaeased.) We also assured the RVN that we would defend them against overt NVA aggression but did not live up to our promise. The test of its success was the ARVN defense against the 1972 Easter Offensive where they did quite well with limited but important assistance from the US mostly in the air.

Cheers

JohnT