Dan Lindley and Ryan Schildkraut1

IWR Wars includes all variables dependent on the primary key War#. In other words, variables that are only associated with a specific war, and not the states involved in that war, are stored here. For example, the beginning and ending years of the war are in IWR Wars, not the beginning and ending dates of participation for each state involved.

IWR States includes data on each state involved in a war. The data for state fatalities and duration are here.

IWR StateWarYears includes the capability level of each state for each year they are involved in a war. This table is the key feature of the IWR database. Here is where we integrated data from the COW, MID, and NMC databases For example, COW and MID will show the USA as a participant in the Mexican-American War from 1846-1848, but includes no measurement for its capability index during those years. The NMC provides the USA capability score for 1846-1848, but does not indicate that these are war years. In this table, we pull this data together. The capabilities numbers stored here are used to calculate Cap(I) and Cap(T) in IWR WarYears. This table also shows the role of each state for each year (i.e. initiator, target, joiner, etc).

IWR WarYears includes data for each year of every war. In this table are the aggregate capabilities of the initiating side and target side for each year of the war.

Because IWR accounts for all possible variable dependencies, no additional tables need to be created to insert new data. As these tables are already keyed by war, by states in the war, by state for each war year, and by years of every war, the IWR schema allows for seamless integration of new data.

II. IWR Variables

This section explains the coding of each IWR variable. For the methodologies used to arrive at the coding, please see section III of this appendix.

IWR Wars

War#: Identification number for each war. COW data.

War Name: Name of each war. COW data.

YrBeg: Beginning year of each war. COW data.

YrEnd: Ending year of each war. COW data.

RelCap(I) - Day One: The relative capabilities of initiator(s) to target(s) on the first day of the war. RelCap(I) = Cap(I)/[Cap(I)+Cap(T)] . Calculated from NMC 3.0.

COW Outcome: War outcome as coded by COW.

MID Outcome: War outcome as coded by MID.

Dyadic: Is this war a one-on-one fight? (No = 0, Yes = 1).

Joiners: Are joiners involved in the war? (No = 0; Offensive joiners = 3; Defensive joiners = 4; Joiners on both sides = 5). Calculated per decision rules described below.

Coalitions: Is there more than one state on the either side on day one of the war? (Initiator coalition = 1; Target coalition = 2; Both = 5). Calculated per decision rules described below.

War Duration: Duration, in days, of the war. Calculated using COW data.

Fatalities(I): Total fatalities suffered by the initiating side and its joiners over the course of the war. Calculated using COW data.

Fatalities(T): Total fatalities suffered by the target side and its joiners over the course of the war. Calculated using COW data.

Cap(I) - Day One: Aggregate capability of the initiating side on the first day of the war. Calculated using NMC CINC data.

Cap(T) - Day One: Aggregate capability of the target side on the first day of the war. Calculated using NMC CINC data.

RelCap(I) – Day End: The relative capabilities of the initiating side to the target side on the final day of the war. Calculated from NMC.

Cap(I) – Day End: The aggregate capabilities of the initiating side on the final day of the war. Calculated from NMC.

Cap(T) – Day End: The aggregate capabilities of the target side on the final day of the war. Calculated from NMC.

RelMilCap(I) – Day One: The relative military capabilities of initiator(s) to target(s) on the first day of the war. RelMilCap(I) = MilCap(I)/[MilCap(I)+MilCap(T)]. Calculated from NMC. See discussion below on how MilCap figures are derived.

MilCap(I) – Day One: The aggregate military capabilities of the initiating side on the first day of the war. Calculated from NMC.

MilCap(T) – Day One: The aggregate military capabilities of the target side on the first day of the war. Calculated from NMC.

RelE/S(I) – Day One: The relative ratio of expenditures per soldier for iniator(s) to target(s) on the first day of the war. ‘RelE/S(I)’ = ‘E/S(I)’/[‘E/S(I)’+’E/S(T)’] Calculated from NMC. See discussion below on how E/S figures are derived.

E/S(I) – Day One: The expenditures per soldier ratio for initiator (s)on the first day of the war. Calculated from NMC.

E/S(T) – Day One: The expenditures per soldier ratio for target(s)on the first day of the war. Calculated from NMC.

MilEx(I) – Day One: The aggregate military expenditures of initiator(s) as of the first day of the war. Calculated from NMC.

MilEx(T) – Day One: The aggregate military expenditures of target(s) as of the first day of the war. Calculated from NMC.

MilPer(I) – Day One: The aggregate military personnel of initiator(s) as of the first day of the war. Calculated from NMC.

MilPer(T) – Day One: The aggregate military personnel of target(s) as of the first day of the war. Calculated from NMC.

IWR States

War#: Identification number for each war. COW data.

StAbb: State abbreviation. COW data.

Fatalities: Number of fatalities suffered by this state in this war. COW data.

State Duration: Duration, in days, of this state’s involvement in this war. COW data.

IWR StateWarYears

War#: Identification number for each war. COW data.

StAbb: State abbreviation. COW data.

Year: Specific year of this state’s involvement. COW data.

Role: The role of this state in the war.^{^[1]} Initiator = 1; Target = 2; Offensive joiner = 3, Defensive joiner = 4. Coded per decision rules listed below.

Cap: A measure of a state’s capabilities. We use the CINC (Composite Index of National Capabilities) score from NMC. See the NMC documentation for notes on how the CINC score is derived.

MilCap: The state’s military capabilities for this year. Calculated with data from NMC as explained below.

E/S: This state’s ratio of expenditures per soldier for this year. Calculated using NMC

MilEx: This state’s military expenditures for this year. NMC data.

MilPer: This state’s military personnel for this year. NMC data.

IWR WarYears

War#: Identification number for each war. COW data.

Year: Specific year of this war. COW data.

RelCap(I) - Day One: The relative capabilities of initiator(s) and their joiners to target(s) and their joiners for this year of the war. Calculated from Cap (see below, and NMC documentation).

Cap(I) - Day One: Aggregate capability of the initiating side for this year of the war. Calculated using NMC data.

Cap(T) - Day One: Aggregate capability of the target side for this year of the war. Calculated using NMC data.

RelMilCap(I): The relative military capabilities of initiator(s) and their joiners to target(s) and their joiners for this year of the war. Calculated from NMC. See discussion below on how MilCap figures are derived.

MilCap(I): The aggregate military capabilities for initiator(s) and their joiners for this year of the war. Calculated from NMC. See discussion below on how MilCap figures are derived.

MilCap(T): The aggregate military capabilities for target(s) and their joiners for this year of the war. Calculated from NMC. See discussion below on how MilCap figures are derived.

RelE/S(I): The relative ratio of expenditures per soldier for iniator(s) and their joiners to target(s) and their joiners for this year of the war. Calculated from NMC. See discussion below on how MilCap figures are derived.

E/S(I): The expenditures per soldier ratio for initiator(s) and their joiners for this year of the war.

E/S(T): The expenditures per soldier ratio for targets(s) and their joiners for this year of the war.

MilEx(I): The aggregate military expenditures of initiator(s) and their joiners for this year of the war. Calculated from NMC.

MilEx(T): The aggregate military expenditures of targets(s) and their joiners for this year of the war. Calculated from NMC.

MilPer(I): The aggregate military personnel of initiator(s) and their joiners for this year of the war. Calculated from NMC.

MilPer(T): The aggregate military personnel of targets(s) and their joiners for this year of the war. Calculated from NMC.

III. Methodologies and Decision Rules

Wars:

The IWR database includes all wars from the COW dataset.

The latest version of MID (3.02, released in 2003) includes wars through 2001. However, the current version of COW (released in 1997) only includes wars through 1991 (the Gulf War). Because our coding relies on a combination of data from COW and MID, data on a war must exist in each dataset. Therefore, we are unable to include those wars in MID that do not exist in COW (N = 3).

Participants:

IWR includes data for all COW participants for each war. If a state is part of MID, but not COW, it is not included in IWR.

Roles: Initiators, Targets, Joiners

Initiators:

There were three possible sources to code IWR Initiators: COW Initiator, MID Initiator, and MID Revisionist. COW defines the initiator as the side that “made the first attack in strength” (Singer and Small 1972, 366). For MID, the initiator (Side A + Originator = attacking originator in MID) is “the state that takes the first militarized action.” The MID Revisionist coding signifies “the state or states that sought to overturn the status quo ante.” (Jones, Bremer, Singer 1996, 178; see also Bennett and Stam 2003, 49-51).

We primarily used the MID Revisionist state coding to determine initiators. We do not use MID or COW Initiator to code IWR Initiators because they only indicate which state moved in force or took the first militarized action, which is not necessarily the same thing as wanting to start a war. For our purposes, MID Revisionist is a better indicator of IWR Initiator because it indicates the state that actively pursues war and/or heightens tensions between the sides. Revisionists are more likely to be the true aggressors in the conflict.

In some cases, however, both sides of the dispute are coded as revisionists (ie. each has the goal of changing the status quo). In these cases, we used the COW Initiator to break the tie and choose the IWR Initiator. COW’s coding of the initiator using force “in strength” is a more persuasive way to break the tie than MID’s “first militarized action.” By coding closer to who fired the first shot rather than who moved in strength, MID Initiator makes Poland appear to start World War II, and Ethiopia start a war against Italy in 1935.

Section IV details how many times the databases disagree about which state started a war, and shows which war MID codes both sides as Revisionist. For example, in the 79 wars in IWR database, COW and MID disagree 22 times about which state initiated a war.

All states which fought on the side of the IWR Initiators on day one of the conflict are also considered initiators within a coalition, not joiners. Any state joining after day one of the conflict is considered a joiner (see below). Dates are from COW. For our purposes, we seek to determine how the actions by non-day one states affect the outcomes of wars.

For sides, we used the MID Side(A) variable to determine shows the states on each side. All states listed as Side(A) are members of the attacking side (per MID definitions). Those states not listed as Side(A) are part of the defending side.

In sum, our decision rules for coding initiators are:

1.) MID Revisionist = IWR Initiator

2.) If both sides are revisionist, or if neither side is revisionist in MID, then COW Initiator = IWR Initiator

3.) A non-revisionist state that allies with the IWR Initiator on Day One of conflict is also an IWR Initiator (within a coalition).

Please consult the end of the technical appendix for a discussion of why coding rules are needed for initiators.

Targets:

In a dyadic war, the target is the state that is not the IWR Initiator. To determine the targets in coalition and joiner wars, we first must find out which states are on which side. To do this, we use the MID Side A variable which codes as 0 for not Side A and 1 for Side A (Side A is the side that “takes the first militarized action,” Jones, Bremer, Singer 1996, 178). After we determine the IWR Initiator (above), all states that share the IWR Initiator’s Side A code are on the initiator’s side. All states that do not share the code are on the defender’s side. As IWR Initiators are primarily MID Revisionists and are not necessarily MID Initiators, IWR Initiators may or may not be on Side A.

All states which fight on the side of the IWR targets on day one of the conflict are also considered targets within a coalition, not joiners. Dates are from COW.

Joiners:

Joiners are all states who enter the conflict after day one of the conflict. Offensive joiners are on the side of the IWR Initiators. Defensive joiners are on the side of the targets. Sides are determined as specified under the above section on Targets. Dates are from COW.

In World War II (#139), four states switch sides during the conflict. The IWR coding only allows a state to have one role for a given year. Therefore, we use the following decision rule:

1.) A state must switch sides prior to June 1 for its role to change for that year. For example, if state X is an offensive joiner who is conquered by the target side on June 2, state X is listed as an offensive joiner for that year.

Outcome:

The IWR data includes both COW and MID outcomes, and we give results as coded by each database. Therefore, we do not need to choose between COW and MID when their outcome coding varies. For example, COW codes winners in 48 of the 79 wars, while MID has 39.

If a war’s outcome in MID is coded as “Yield by Side A”, we consider this a clear loss for initiators because they have capitulated to their targets and have failed to achieve pre-war goals. “Yield by Side A” outcomes are treated differently from Stalemate, Compromise, and Unclear outcomes in MID because they involve a clear submission by the initiators. We code the Stalemate, Compromise, and Unclear in MID as “Other” in the relevant tables, and consider them comparable to the TIE coding in COW. The wars in which we have coded MID outcomes “Yield by Side A” as Losses are:

#83: Sino-Russian War; #199: Iran-Iraq War; #202: Falklands War.

MilCap and E/S:

To find a state’s MilCap for a given year, we calculate each state’s proportion of all states’ military expenditures for that year average and each state’s proportion of all states’ military personnel for that year. We then average the two proportions to yield MilCap. Comparing one state’s average proportions to another state’s average proportions yields their relative MilCaps. We use the NMC variables MilEx and MilPer for expenditures and personnel. Expenditure per Soldier (E/S) divides Mil/Ec by MilPer. If data for military expenditure or personnel does not exist, we cannot perform MilCap analysis. Out of 79 wars, MilEx and MilPer data for either the initiators or targets do not exist for 32 wars. These instances are coded as -9 in the data.

To calculate the E/S per side per year, we divide the aggregate MilEx for all states on that side for that year by the aggregate MilPer for all state’s on that side for that year.

IV. Why Coding Rules are Needed for Initiators

Coding Rules are needed because the COW and MID databases disagree so often on who initiated wars. They also disagree on outcomes, but since we report both COW and MID outcomes, we do not need coding rules for outcomes. As the following tables show, if we did not have coding rules for initiators and had to report on win rates for four different codings of initiators instead of one, we would need eight tables instead of two.

Current Table System

IWR Initiator

Table 1: COW Outcomes

Table 2: MID Outcomes

Table System Needed with no Coding Rules for Initiators
IWR Initiator	MID Revisionist	MID Initiator	COW Initiator
Table 1: COW Outcomes	Table 3: COW Outcomes	Table 5: COW Outcomes	Table 7: COW Outcomes
Table 2: MID Outcomes	Table 4: MID Outcomes	Table 6: MID Outcomes	Table 8: MID Outcomes

The following table from sheet T3 of the Tables, Graphs, and Calculations Excel Workbook shows the extent of disagreement between the databases on initiators.

*There are 22 wars where COW Initiator and MID Initiator do not match: 10, 16, 22, 55, 67, 85, 91, 100, 112, 118, 127, 136, 139, 157, 160, 166, 169, 172, 178, 202, 205, and 208 (COW War #s).

*There are 17 wars where there is no overlap between the MID Revisionist and the COW Initiator: (ie. no MID Revisionist is a COW Initiator): 19, 22, 28, 49, 58, 85, 91, 97, 103, 118, 147, 157, 163, 166, 169, 175, and 205.

*The IWR Initiator differs from the COW Initiator in 16 wars: 16, 19, 28, 49, 58, 85, 97, 103, 130, 147, 157, 163, 166, 169, 175, and 205.

*The IWR Initiator differs from the MID Initiator in 23 wars: 10, 19, 28, 49, 58, 67, 91, 97, 103, 112, 118, 127, 130, 136, 139, 147, 160, 163, 172, 175, 178, 202, and 208. The ten bolded wars indicate where IWR disagrees with both COW and MID Initiator coding.

Although there are good reasons for these situations, some additional confusion may result from the fact that:

*There are 9 wars in which both sides of the conflict are deemed Revisionist by MID: 64, 88, 109, 124, 125, 133, 136, 151, and 160.

*There are 18 wars where the MID Revisionist is not the MID Initiator: 10, 19, 28, 49, 55, 58, 67, 97, 103, 127, 139, 147, 163, 172, 175, 178, 202, and 208.

¹ Contact information: Dan Lindley Assistant Professor, Department of Political Science, 448 Decio Hall, University of Notre Dame, Notre Dame, IN 46556. Phone: 574-631-3226; Fax: 574-631-8209; Email: dlindley@nd.edu; Webpage: http://www.nd.edu/~dlindley/; Ryan Schildkraut, Student, University of Minnesota Law School, Walter F. Mondale Hall, 229 19th Avenue South, Minneapolis, MN 55455, (612)702-4907, schil131@umn.edu . Dan Lindley is the author to use for correspondence regarding this article. Comments welcome. All data and technical appendix available on request or via the dlindley webpage above. Key methodological points are summarized in the text, and for the purpose of journal review, this technical appendix is included. The appendix is not necessary for understanding the article.

Our thanks to David Campbell, Emma Cohen de Lara, Katherine Jeter, Lauren Kimaid, Garrick Merlo, Adam Shanko, Mariana Sousa, James Thompson, Paul Vasquez, Jennifer Wiemer as well as to numerous panel discussants and other commenters at conferences. The University of Notre Dame Laboratory for Social Research and the Office of Faculty Research also supported this project.

^{^[1]} Note that a very small number of states actually change roles over the course of the war. For example, in World War II (War# 139), there are two entries for France – offensive joiner and defensive joiner. France was quickly conquered by Nazi Germany, then liberated by the allied forces. Technically, they served both sides during different periods of the war.