Bayesian inference for a Lanchester type combat model

We undertake inference for a stochastic form of the Lanchester combat model. In particular, given battle data, we assess the type of battle that occurred and whether or not it makes any difference to the number of casualties if an army is attacking or defending. Our approach is Bayesian and we use modern computational techniques to fit the model. We illustrate our method using data from the Ardennes campaign. We compare our results with previous analyses of these data by Bracken and Fricker. Our conclusions are somewhat different to those of Bracken. Where he suggests that a linear law is appropriate, we show that the logarithmic or linear‐logarithmic laws fit better. We note however that the basic Lanchester modeling assumptions do not hold for the Ardennes data. Using Fricker's modified data, we show that although his “super‐logarithmic” law fits best, the linear, linear‐logarithmic, and logarithmic laws cannot be ruled out. We suggest that Bayesian methods can be used to make inference for battles in progress. We point out a number of advantages: Prior information from experts or previous battles can be incorporated; predictions of future casualties are easily made; more complex models can be analysed using stochastic simulation techniques. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 541–558, 2000     

Note on “An Optimal Recursive Method for Various Inventory Replenishment Models with Increasing Demand and Shortages” by Teng et al.

In a recent paper, Teng, Chern, and Yang consider four possible inventory replenishment models and determine the optimal replenishment policies for them. They compare these models to identify the best alternative on the basis of minimum total relevant inventory costs. The total cost functions for Model 1 and Model 4 as derived by them are not exact for the comparison. As a result, their conclusion on the least expensive replenishment policy is incorrect. The present article provides the actual total costs for Model 1 and Model 4 to make a correct comparison of the four models. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 602–606, 2000     

Monte Carlo estimation of the maximal flow distribution with discrete stochastic arc capacity levels

This article describes a highly efficient Monte Carolo sampling plan for estimating ordinates of the complementary distribution function of the maximal s-t flow in a directed network with source node s, terminal node t and whose arcs assume random capacities. Communication, electric power, transportation, and water distribution systems fit this representation. The article derives point estimates and interval estimates that hold for finite sample sizes, and shows the extent to which the proposed technique saves time, as compared to crude Monte Carlo sampling, in achieving a specified accuracy.     

A theoretical justification for an increasing average failure rate strength distribution in fibrous composites

A general model for the failure of fibrous composite materials is described. It is shown to contain some of the well-known models in the literature. The composite material is viewed as a coherent system of independent identically distributed component strengths. Under the assumption that the applied load is redistributed “homotonically” to the unfailed components upon the failure of a component (an individual fiber segment) and that the distributions of component strengths are IFRA, it is shown that the system (composite) strength distribution is also IFRA. Examples are given using carbon reinforced composite data to illustrate the IFRA property.     

Scheduling prowler training

The U.S. Navy Prowler aircraft is designed for electronic surveillance and countermeasures. In this paper, we describe the problem of scheduling Prowler crew training, and we present two integer programming models to solve it. The first model maximizes the number of aviators trained above 75% in each mission area, subject to the available number of flights, over a single month. The second model distinguishes peacetime from mobilization, and minimizes the number of flights done in mobilization subject to the available number of flights in peacetime. Our models distinguish different types of crew and allow more than one qualification to be earned on a given flight. We give numerical results using real data, comparing our results to the actual readiness of a squadron. We found that crew readiness of Prowler squadrons can be increased by 10%, simply by better scheduling. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 289–305, 2003.     

An Unlikely Alliance: Portuguese and South African Airpower in Angola, 1968–1974

The war that Portugal was obliged to fight in Africa began in 1961 and immediately stretched the resources of its armed forces. Nowhere was this thinness more apparent than in policing the vast territory of Angola. The east and southeast of Angola were particularly vulnerable, as the area was a vast, sparsely populated region characterised by enormous featureless plains or chanas covered in tall grass and broken by an extensive river system and mountainous forests. The only military solution to policing these immense spaces was aviation and specifically the helicopter that could carry troops into battle, protect them with a gunship and bring them home when the operation was concluded. The immediate problem for the Portuguese Air Force (Força Aérea Portuguesa or FAP) in Angola and elsewhere was a scarcity of helicopters. The solution was an alliance with South Africa, which had a strong inventory of Alouette IIIs, to help in policing the east. This move was likewise in the interest of South Africa, as its threat came from Zambia through south-eastern Angola. This article examines the strategic and tactical development of this unusual, cross-cultural alliance and the symbiotic relationship that resulted in destruction of the enemies of both in Angola.     

An Investigation of the Weights of Pattern 1907 Bayonets made in the UK around the First World War Period

The standard issue bayonet of the British Army immediately preceding and during the First World War was the Pattern 1907. This was manufactured at different times and in varying numbers during that period by one official body, the Royal Small Arms Factory at Enfield, and by five private contractors. These bayonets were made according to published official specifications issued by the War Department and based on a ‘pattern example’ provided by the Royal Small Arms Factory. The specifications indicate, inter alia, the quality of metal used in making the bayonets, methods of inspection and proofing, and the required maximum and minimum weight range of the completed bayonet. However, examination of a series of these bayonets in a private collection suggested that their weights varied considerably from the mid-point values of the allowed weight ranges in the original and amended specifications (16.5 oz. and 17 oz., respectively). To establish if this was a common feature among this class of bayonet as opposed to a chance factor, the weights of other surviving Pattern 1907 bayonets were determined and compared to establish the degree of variance from the official specifications as originally set out by the Royal Small Arms Factory. Seventy-six percent of the 142 bayonets surveyed were found to be above the mid-point of the allowed weight range given in the amended manufacturing specifications, with many being at the upper end of the allowed range. This is a statistically unusual result. It is speculated that the target weight may have been deliberately set higher by the individual manufacturers to eliminate the possibility of rejection of any underweight bayonets by the Royal Small Arms Factory inspectors and so a refusal of acceptance and payment for the work.     

TWENTY YEARS OF CYBERWAR

For many years after its introduction in the early 1990s, the cyberwar concept - which outlined a new mode of conflict that would emphasize disruption of information systems and flows - was given little credence. Over the past several years, however, cyberwars of both irregular and somewhat more conventional types have erupted (e.g., see respectively Estonia in 2007 and Georgia in 2008). Global awareness of cyberwar has risen sharply, and many nation-states are preparing their defenses, as well as their capabilities for mounting offensive operations. The American military's declaration in 2011 that cyberspace is a 'warfighting domain' highlights a need to explore the ethical implications and nuances of cyberwar. This article finds that classic jus ad bellum constructs come under great pressure from cyberwar, while jus in bello concerns may prove more manageable. Another key theme is that disproportionate attention is given to the notion of employing cyberwar 'strategically' (i.e., to strike directly at other nations' infrastructures), where its use is less likely to achieve 'victory' and is more problematic ethically. Instead, a focus on the application of cyberwar techniques in battle may lead to shorter, less bloody, 'more ethical' conflicts.     

An alliance between Cyprus and Greece: assessing its partners’ relative security contribution

The issue that this paper tackles is the assessment of the relative security benefits that Cyprus and Greece derive in the context of their cooperation on defence matters. This form of cooperation, known as the ‘Integrated Defence Space Doctrine’, aims at defending their interests in the Aegean Sea and the broader East Mediterranean theatre. The paper relies heavily on earlier research on this topic, which deals with the Greek–Cypriot alliance facing an arms race against Turkey, and uses a coefficient especially designed to assess the optimal levels of security and the associated defence expenditure of the two allies. A comparison of the relative security coefficient values for the two allies suggests that the security benefit that Greece derives thanks to its alliance with Cyprus exceeds the corresponding Cypriot benefit by far. Given the importance assigned to human resources by this index, in conjunction with the demographic problems of Greece, this conclusion justifies the recent Greek defence policy revision, emphasizing quality, capital equipment and flexibility of forces. This revision aims at satisfying the security requirements of the alliance and the increasing demands of an arms race against Turkey.