Wartime logistics model for multi‐support unit location–allocation problem with frontline changes

• Author: Ilkyeong Moon,Hyejung Koo
• Published date: 01 November 2020
• DOI: http://doi.org/10.1111/itor.12616
• Date: 01 November 2020

Intl. Trans. in Op. Res. 27 (2020) 3031–3055

DOI: 10.1111/itor.12616

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Wartime logistics model for multi-support unit

location–allocation problem with frontline changes

Hyejung Kooaand Ilkyeong Moonb,∗

aJoint ForcesMilitary University, Ministry of National Defense, Daejeon 34059, Republic of Korea

bDepartment of Industrial Engineering and Institute for Industrial Systems Innovation, Seoul National University,

Seoul 08826, Republic of Korea

E-mail: hyejung1982@gmail.com [Koo]; ikmoon@snu.ac.kr [Moon]

Received 23 December 2017; receivedin revised form 1 October 2018; accepted 6 November 2018

Abstract

To reflect a realistic, changing front line, wartime logistics are illustrated by a dynamic location–allocation

model. In this paper,a mixed integer programming (MIP) model is developed for use in deciding the timing of

unit relocation for continuousresupply, safe locations for support units, and delivery amounts that minimize

total risk to the logistics service. Total risk in wartime logistics is represented by unsatisfied demand, hazard

at the support site, and the number of relocations. The proposed MIP model reflects realistic factors in

battle situations,such as maximum distance, vehicle capacity, basic load carried by combatunits, and limited

supplies during unit relocation. Furthermore, special operators for crossover and mutation are developed to

maintain feasibility of possible solutions, and an efficienthybrid genetic algorithm is proposed to find optimal

and near-optimal solutions.

Keywords:dynamic location–allocation problem; hybridgenetic algorithm; mixed integer programming; wartime logistics

system

1. Introduction

To secure line of communications (LOCs) and continuous supplies are recognized as important

factors in wartime success. The supply chain of the Republic of Korea (ROK) Army features a

multilevel structure that reserves inventory for emergencies, such as during isolation or urgent

deployment. Military commodities are classified into nine categories such as food, ammunition,

maintenance item, and so forth. One type of commodity with similar attributes, which is defined

as a class, has a different priority for transport compared to other types of commodities. The

ROK Army logistics structure is composed of a hierarchical organization consisting of supply

∗Corresponding author.

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International Transactionsin Operational Research C

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3032 H. Koo and I. Moon / Intl. Trans. in Op. Res. 27 (2020) 3031–3055

and transportation, maintenance, and ammunition. Materials in one type of class may be handled

by more than two support units, and a support unit may transport materials of more than one

class. Support units analyze previous logistics requirements, estimate current demand, and deliver

materials.Combat units in engagement require resupply and relocatetheir bases to the site of relative

advantage over the enemy for taking the initiative as situations evolve.

The provision of supplies for initiatives at the right time, in the right place, and with appropriate

quantity is an integral part of success in wartime logistics. The main decisions involve the timing of

relocations to block risks to increasingly long LOCs, determination of a new position to relocate

that reduces risk from enemy threats, the amount of supplies that satisfy daily demand. Support

units need flexibility to maintain successive supply operations by keeping reserves and adjusting

daily supplies as dictated by uncertainties in the battlefield. Frontline changes resulted from the

engagement and damage to friendly forces are the main causes of uncertainties in wartime logistics

and can lead to problems in establishing future operations. Uncertainties in the battlefield result

from difficulties in predicting an enemy attack. The location of combat units and the demand for

supplies change with levels of enemy hostility. Hence, to establish continuous supply operations,

commanders of support units must consider many factors when deciding when and where to move.

To evaluate the performance of a military logistics services, one must simultaneously analyze the

geographical advantages of possible locations of support units as well as service levels necessary

to meet demand. Therefore, the focus of this paper is on a location–allocation problem in which

the optimal location and delivery schedule are determined at the same time. The proposed model,

which includes evaluation factors, is practical for deciding the time of unit relocation, the location

that minimizes risk from enemy threats, and the delivery amounts that maximize service levels of a

wartime logistics support system. The optimal supply system suggested in this paper might serve as

a scientific decision tool that commanders use to make determinations quickly.

Although the location problem is widely studied in the private sector, to adapt it to the army

logistics is difficult because of the special characteristics of wartime logistics. Sim et al. (2013)

summarized the differences between military and commercial supply chains in terms of goals,

objectives, key performance indicators, procurement criteria, demand characteristics, supply chain

networks, and processes for product acquisition. Although the military logistics system aligns with

an integrated logistics system, the frequently changing environment makes adaptation a challenge.

Sim et al. (2013) suggested a mathematical model that minimizes the total cost of the supply chain

to determine the optimal location and number of facilities to open. As Sim et al. (2013) pointed out,

the goal of the military supply chain is to minimize inventory shortages rather than to minimize

inventory holding costs. Also, the demand during wartime is both unstable and unforecastable,

supply points are changeable, and material has priority over other products. In these ways, military

logistics systems feature several characteristics that differ from those of a private-sector supply

chain.

First, for military logistics, support for a successful operational plan is much more important

than total cost reduction. To the contrary, improvements to the private-sector supply chain are

aimed at maximizing the profit of the enterprise or minimizing the cost. Hence, the purpose of

the private-sector supply chain is fundamentally different from that of wartime logistics. Therefore,

many researchers have shown that, for the military logistics support system, maximizing the total

effectiveness to guarantee a successful operation is more appropriate than the commonly taken

approach of reducing total distribution costs. The information from the second-best solution,

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2018 The Authors.

International Transactionsin Operational Research C

2018 International Federation ofOperational Research Societies