▁troops ) ▁in ▁the ▁S ino - V ietnam ese ▁border ▁region , ▁including ▁one ▁along ▁the ▁coast . ▁It ▁had ▁also ▁increased ▁its ▁landing ▁craft ▁fleet ▁and ▁was ▁period ically ▁st aging ▁am ph ib ious ▁landing ▁exer cis es ▁off ▁H ain an ▁Island , ▁across ▁from ▁Vietnam , ▁thereby ▁demonstr ating ▁that ▁a ▁future ▁attack ▁might ▁come ▁from ▁the ▁sea . ▁ ▁Low - level ▁conflict ▁continued ▁along ▁the ▁S ino - V ietnam ese ▁border ▁as ▁each ▁side ▁conducted ▁art illery ▁shell ing ▁and ▁prob ed ▁to ▁gain ▁high ▁sp ots ▁in ▁the ▁mountain ous ▁border ▁terrain . ▁Border ▁inc idents ▁increased ▁in ▁intensity ▁during ▁the ▁ra iny ▁season , ▁when ▁Be ij ing ▁attempted ▁to ▁ease ▁Vietnam ese ▁pressure ▁against ▁Camb od ian ▁resistance ▁f igh ters . ▁ ▁Since ▁the ▁early ▁ 1 9 8 0 s , ▁China ▁purs ued ▁what ▁some ▁obser vers ▁described ▁as ▁a ▁semi - secret ▁campaign ▁against ▁Vietnam ▁that ▁was ▁more ▁than ▁a ▁series ▁of ▁border ▁inc idents ▁and ▁less ▁than ▁a ▁limited ▁small - scale ▁war . ▁The ▁Vietnam ese ▁called ▁it ▁a ▁" mult if ac et ed ▁war ▁of ▁sab ot age ." ▁H ano i ▁officials ▁have ▁described ▁the ▁assault s ▁as ▁compr ising ▁steady ▁har ass ment ▁by ▁art illery ▁fire , ▁intr us ions ▁on ▁land ▁by ▁inf antry ▁pat rol s , ▁naval ▁intr us ions , ▁and ▁mine ▁plant ing ▁both ▁at ▁sea ▁and ▁in ▁the ▁river ways . ▁Chinese ▁c land est