How did the loss of counting rods affect the understanding of older Chinese algebra?

The decline of Chinese algebraic knowledge between the 14th and 16th centuries was closely linked to the abandonment of counting rods as a primary calculating tool.1

Historically, Chinese mathematical procedures—including the sophisticated "method of the celestial unknown"—relied on a decimal place-value system performed on a counting board. These rods allowed mathematicians to physically manipulate numbers and represent polynomials through positional notation, where the location of a coefficient indicated the power of the indeterminate.123

As the abacus gained popularity and counting rods fell into disuse, the physical instrument that supported these algebraic notations disappeared. Deprived of the counting board, later scholars could no longer interpret the ancient place-value representations, leading to the "method of the celestial unknown" being forgotten by the 17th century. It was not until the 18th century that mathematicians were able to decipher these texts by applying Western algebraic concepts to the ancient Chinese sources.1