The Sea Lines of Communication (SLOCs) are a strategic concept that designates the principal maritime pathways interconnecting global ports, serving as conduits for commercial trade, energy shipments, and naval logistics. These routes are the indispensable arteries of the global economy, accommodating over 90 percent of international trade by volume. The concept originated in late 19th-century naval theory, articulated by U.S. Navy officer Alfred Thayer Mahan in his seminal 1890 work, The Influence of Sea Power Upon History, 1660–1783. Mahan posited that national power hinged on achieving command of the sea to protect these trade lanes, establishing a link between maritime security and great-power endurance.
SLOCs function as the most short, economical, and safe routes for transporting cargo, but they concentrate at vulnerable chokepoints like the Strait of Malacca, Strait of Hormuz, and Bab el-Mandeb Strait. The security of these routes is governed by the United Nations Convention on the Law of the Sea (UNCLOS), adopted in 1982 and in force since 1994. UNCLOS establishes the legal framework for transit passage through straits used for international navigation under Articles 37–44. Related concepts include India's strategic vision of SAGAR (Security and Growth for All in the Region), which emphasizes cooperative security along critical SLOCs.
For India, whose trade is 90-95 percent dependent on sea transport by volume, the stability of the Indian Ocean SLOCs is a crucial lifeline. The security of SLOCs has recently been challenged by non-state actors, such as the Houthi attacks in the Red Sea between 2023 and 2024, which forced major shipping companies to reroute via the Cape of Good Hope. This period, from 2010 to 2024, has seen India's focus on SLOC security transition from a purely naval issue to a broad strategic priority due to heightened great power rivalry in the Indian Ocean Region.