Indonesia is confronting challenges overhauling its aging military despite a spending splurge to face down threats that include a long-running territorial dispute with its biggest trading partner, China.

Incursions by Chinese vessels into waters around the Natuna Islands, between Malaysia and Indonesia, have put Jakarta on alert. The government recently relocated a major naval fleet command to Riau, near the islands, after starting construction on a submarine base last year. It also announced plans to spend $125 billion on new weapons, despite a shrinking defense budget.

But expensive weapons can’t solve all of Indonesia’s defense challenges. Its reliance on several foreign suppliers — including Russia — over the years means its existing hardware is burdened by interoperability problems, said Evan Laksmana, senior research fellow at the Lee Kuan Yew School of Public Policy at the National University of Singapore.