The two li~Nga-s in the ruins of the garbhA-gR^iha of the bhadreshvara complex
The nandin and the bali pItha-s a another site on the bhadreshvara complex
We know little of the early history of the Hindu rulers of champAvatI (modern Vietnam) of the dynasty of shrI-mAravarman. But it is important to understand this to gain insight into the history of the mantra-mArga and pAshupata shaiva matas. mAravarman appears to have reigned in the 2nd century CE as suggested by his Sanskrit inscription. There is evidence that he led a naval attack on the chIna-s to seize the chIna-held province of Tonkin. His much later successor had a border dispute with the chIna-s over the Hoan Sonh mountains. When the negotiations with the chIna-s broke down the champApati invaded Nhut Nam and conquered it from the chIna-s. He was however wounded in this battle and died shortly there after. During his son’s reign the chIna-s of the Han organized a massive invasionary force by land and sea with several new weapons like fire spears and the like and attacked champAvatI. The Hindu ruler faced heavy losses and was forced to retreat from the fertile Nhut Nam province. His son was the great rAja shrI bhadravarman. He retaliated on large scale and inflicted a crushing defeat on the chIna-s. He forced them give up Nhut Nam and continued the invasion into the chIna-held lands to conquer Than Hoa from them.
bhadravarman reigned from 380CE to 413 CE and Sanskrit inscriptions from his reign show that he had learned the recitation of the vedic saMhitA-s and performed vedic rituals. He calls himself a devotee of rudra, and he celebrated the grace of rudra in securing his victory over the chIna-s by building the glorious temple for shiva termed shrI bhadreshvara. Now we know that somewhat later in the far east the main lineage of the mantra-mArga shaiva mata was that of the vAma-srotas of the Cambodian empire with its depiction of tumburu. But the question arises as to what were the affinities of the earlier shaiva-mata at champAvatI. An analysis of the ruins of the bhadreshvara temple at MySon, Vietnam suggest that siddhanta tantras of the Urdhva-srotas along with elements of the pAshupata shaiva were in operation. The key elements of the Urdhvasrotas or the pre-pentafurcation mantra-mArga include the worship of the vidyeshvaras and the li~Nga with a square yoni. Possible performance of the jayAbhisheka as described in the kUrma purANa is an indication of the pAshupata affinities, which was also coevally common in the gupta empire in India. One of the images of an 8-armed shiva in nR^itya are also highly reminiscent of similar depictions in the pAshupata temples in India. Thus, it is clear that multiple waves of mantra-mArga (+pAshupata) shaiva practice moved from India to the Indic civilizations of the East. In this sense the developments there paralleled those on the mainland where different dynasties were associated specifically with different branches of mantra-mArga or pAshupatas.
[It should be kept in mind that the original bhadreshvara complex was renovated repeatedly by the later rulers of champAvatI like rudravarman and shambhuvarman. But the complex today is in poor condition making it difficult to separate the different layers. Further, the Americans with their unsurprising Abrahamistic mindset destroyed a significant portion of the temples in this complex during their invasion of modern Vietnam]