Nevertheless , after these failures the CIA continued its attempts to disrupt the Trail 's activities .
The huge Operation Lam Son 719 attack of February 1971 proved insufficient to sever the supply conduit of the Trail .
After these failures the CIA continued its attempts to disrupt the Trail 's activities .
The huge Operation Lam Son 719 attack of February 1971 proved insufficient to sever the supply conduit of the Trail .