Complex sentence: The battle ended with a near annihilation of the Siamese, all the ships of the Siamese navy were destroyed and only 1,000 of the original expedition survived to escape back across the river into Siam.
Split into simpler sentences: The battle ended with a near annihilation of the Siamese force. All the ships of the Siamese navy were destroyed and only 1,000 of the original expedition survived to escape back across the river into Siam.