Analytical Disruption Thresholds for Classical Inventory Policies Under Maritime Lead Time Uncertainty: Evidence from the Red Sea Shipping Crisis

The 2023–2024 Red Sea shipping crisis rerouted container traffic from the Suez Canal to the Cape of Good Hope, reducing canal tonnage by 82% and extending Asia–Europe transit times by 10–14 days. This paper identifies the disruption severity thresholds at which three classical inventory policies—order-up-to (S), (s,S), and periodic-review (R,S)—transition from stable operation to operational failure. An analytical framework for the order-up-to policy under stochastic lead times is derived, calibrated to UNCTAD transit data, SCFI freight rate indices, and M5 retail demand patterns, and validated against a single-echelon discrete-event simulation. Per-cycle service level agreement between analytical predictions and simulation holds within 3 percentage points across disruption severities k=1.0 to 3.0 (R^2 > 0.99). Three principal findings emerge. First, all three policies breach the 85% cycle service level at disruption severities near k=1.04—equivalent to approximately one additional transit day on a 28-day baseline voyage—demonstrating that no classical policy possesses a meaningful buffer against maritime disruption. Second, probability-based service metrics degrade before expectation-based cost metrics, establishing a metric sensitivity hierarchy with a narrow early-intervention window between service degradation (k≈1.04) and cost doubling (k≈1.11). Third, a reactive base-stock policy with rolling parameter re-estimation recovers the target 91% service level in steady state but is constrained by an adaptation lag of 56–70 days, during which it performs identically to the static policy.