Head-to-head comparisons of military strength are hard to come by.

Global Firepower's 2019 Military Strength Ranking tries to fill that void by drawing on more than 55 factors to assign a Power Index score to 137 countries adding Moldova this year. (Global Firepower appears to have changed its methodology from that of previous lists the 2019, yielding different index numbers.)

The ranking assesses the diversity of each country's weapons and pays particular attention to their available manpower. Geography, logistical capacity, available natural resources, and the status of local industry are also considered.

Recognized nuclear powers receive a bonus, but their nuclear stockpiles are not factored into the score. Landlocked countries are not docked for lacking a navy, but countries with navies are penalized if their fleets lack diversity. (Helicopter carriers are included alongside traditional fleet carriers in Global Firepower's ranking.)

NATO countries get a slight bonus because the alliance theoretically shares resources, but in general, a country's current political and military leadership was not considered (though financial health and stability are).

The top power index score is 0.0000, which is "realistically unattainable," according to Global Firepower. The closer they are to this number, the more powerful their military is.

Per these criteria, these are the 25 most powerful militaries in the world:

25. Saudi Arabia

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Umit Bektas / REUTERS

Power Index rating: 0.4268

Total population: 33,091,113

Total military personnel: 230,000 (estimated)

Total aircraft strength: 848; ranks 12th out of 137 countries

Fighter aircraft: 244; ranks 12th

Combat tanks: 1,062 (ranks 24th)

Total naval assets: 55

Defense budget: $70 billion

24. Poland

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Kacper Pempel/Reuters

Power Index rating: (NATO member) 0.4059

Total population: 38,420,687

Total military personnel: 105,000 (estimated)

Total aircraft strength: 469 (ranked 27th of 137)

Fighter aircraft: 93 (ranked 26th)

Combat tanks: 1,100 (ranked 23rd)

Total naval assets: 83

Defense budget: $9.36 billion

23. Vietnam

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REUTERS/Kham

Power Index rating: 0.3988

Total population: 97,040,334

Total military personnel: 5,482,000 (estimated)

Total aircraft strength: 318 (ranked 33rd out of 137)

Fighter aircraft: 108 (ranked 21st)

Combat tanks: 2,575 (ranked 28th)

Total naval assets: 65

Defense budget: $3.365 billion

22. Taiwan

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Reuters

Power Index rating: 0.3956

Total population: 23,545,963

Total military personnel: 1.89 million (estimated)

Total aircraft strength: 837 (ranked 13th out of 137)

Fighter aircraft: 286 (ranked 9th)

Combat tanks: 1,885 (ranked 17th)

Total naval assets: 87

Defense budget: $10.725 billion

21. Canada

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Rob Kunzing/NATO

Power Index rating: (NATO member) 0.3941

Total population: 35,881,659

Total military personnel: 94,000 (estimated)

Total aircraft strength: 384 (ranked 31st of 137)

Fighter aircraft: 53 (ranked 38th)

Combat tanks: 80 (ranked 79th)

Total naval assets: 63

Defense budget: $21.2 billion

20. Spain

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Photo by 1st German/Netherlands Corps

Power Index rating: (NATO member) 0.3921

Total population: 49,331,076

Total military personnel: 139,500 (estimated)

Total aircraft strength: 522 (ranked 23rd out of 137)

Fighter aircraft: 136 (ranked 18th)

Combat tanks: 327 (ranked 51st)

Total naval assets: 46; one aircraft carrier

Defense budget: $11.6 billion

19. Australia

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Hugh Gentry/REUTERS

Power Index rating: 0.3277

Total population: 23,470,145

Total military personnel: 79,700 (estimated)

Total aircraft strength: 467 (ranked 28th out of 137)

Fighter aircraft: 78 (ranked 27th)

Combat tanks: 66 (ranked 86th)

Total naval assets: 47; two aircraft carriers

Defense budget: $26.3 billion

18. North Korea

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REUTERS/KCNA

Power Index rating: 0.3274

Total population: 25,381,085

Total military personnel: 7.58 million (estimated)

Total aircraft strength: 949 (ranked 11th out of 137)

Fighter aircraft: 458 (ranked 5th)

Combat tanks: 6,075 (ranked 4th)

Total naval assets: 967

Defense budget: $7.5 billion

17. Israel

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Ariel Schalit/AP

Power Index rating: 0.2964

Total population: 8,424,904

Total military personnel: 615,000 (estimated)

Total aircraft strength: 595 (ranked 18th out of 137)

Fighter aircraft: 253 (ranked 11th)

Combat tanks: 2,760 (ranked 8th)

Total naval assets: 65

Defense budget: $19.6 billion

16. Indonesia

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Beawiharta Beawiharta/REUTERS

Power Index rating: 0.2804

Total population: 262,787,403

Total military personnel: 800,000 (estimated)

Total aircraft strength: 451 (ranked 30th out of 137)

Fighter aircraft: 41 (ranked 43rd)

Combat tanks: 315 (ranked 52nd)

Total naval assets: 221

Defense budget: $6.9 billion

15. Pakistan

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Mohsin Raza/Reuters

Power Index rating: 0.2798

Total population: 207,862,518

Total military personnel: 1,204,000 (estimated)

Total aircraft strength: 1,342 (ranked 7th out of 137)

Fighter aircraft: 348 (ranked 7th)

Combat tanks: 2,200 (ranked 13th)

Total naval assets: 197

Defense budget: $7 billion

14. Iran

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Reuters

Power Index rating: 0.2606

Total population: 83,024,745

Total military personnel: 873,000 (estimated)

Total aircraft strength: 509 (ranked 24th out of 137)

Fighter aircraft: 142 (ranked 17th)

Combat tanks: 1,634 (ranked 18th)

Total naval assets: 398

Defense budget: $6.3 billion

13. Brazil

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REUTERS/Ricardo Moraes

Power Index rating: 0.2487

Total population: 208,846,892

Total military personnel: 1,674,500 (estimated)

Total aircraft strength: 706 (ranked 16th out of 137)

Fighter aircraft: 43 (ranked 42nd)

Combat tanks: 437 (ranked 40th)

Total naval assets: 110

Defense budget: $29.3 billion

12. Egypt

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Associated Press

Power Index rating: 0.2283

Total population: 99,413,317

Total military personnel: 920,000 (estimated)

Total aircraft strength: 1,092 (ranked 9th out of 137)

Fighter aircraft: 211 (ranked 13th)

Combat tanks: 2,160 (ranked 14th)

Total naval assets: 319; two aircraft carriers

Defense budget: $4,4 billion

11. Italy

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REUTERS/Fadi Ghalioum

Power Index rating: (NATO member) 0.2277

Total population: 62,246,674

Total military personnel: 357,000 (estimated)

Total aircraft strength: 831 (ranked 14th out of 137)

Fighter aircraft: 94 (ranked 25th)

Combat tanks: 200 (ranked 60th)

Total naval assets: 137; five aircraft carriers

Defense budget: $29.2 billion

10. Germany

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REUTERS/Fabrizio Bensch

Power Index rating: (NATO member) 0.2097

Total population: 80,457,737

Total military personnel: 208,641 (estimated)

Total aircraft strength: 613 (ranked 17th out of 137)

Fighter aircraft: 122 (ranked 20th)

Combat tanks: 900 (ranked 26th)

Total naval assets: 81

Defense budget: $49.1 billion

9. Turkey

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Umit Bektas/Reuters

Power Index rating: (NATO member) 0.2089

Total population: 81,257,239

Total military personnel: 735,000 (estimated)

Total aircraft strength: 1,067 (ranked 10th out of 137)

Fighter aircraft: 207 (ranked 14th)

Combat tanks: 3,200 (ranked 7th)

Total naval assets: 194

Defense budget: $8.6 billion

8. United Kingdom

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Sgt. Seth Plagenza/US Army

Power Index rating: (NATO member) 0.1797

Total population: 65,105,246

Total military personnel: 233,000 (estimated)

Total aircraft strength: 811 (ranked 15th out of 137)

Fighter aircraft: 129 (ranked 19th)

Combat tanks: 331 (ranked 49th)

Total naval assets: 76; one aircraft carrier

Defense budget: $47.5 billion

7. South Korea

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AP

Power Index rating: 0.1761

Total population: 51,418,097

Total military personnel: 5,827,150 (estimated)

Total aircraft strength: 1,614 (ranked 5th out of 137)

Fighter aircraft: 406 (ranked 6th)

Combat tanks: 2,654 (ranked 9th)

Total naval assets: 166; one aircraft carrier

Defense budget: $38.3 billion

6. Japan

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Yuya Shino/REUTERS

Power Index rating: 0.1707

Total population: 126,128,156

Total military personnel: 303,157 (estimated)

Total aircraft strength: 1,572 (ranked 6th out of 137)

Fighter aircraft: 297 (ranked 8th)

Combat tanks: 1,004 (ranked 25th)

Total naval assets: 131; four aircraft carriers

Defense budget: $47 billion

5. France

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Associated Press

Power Index rating: (NATO member) 0.1584

Total population: 67,364,357

Total military personnel: 388,635 (estimated)

Total aircraft strength: 1,248 (ranked 8th out of 137)

Fighter aircraft: 273 (ranked 10th)

Combat tanks: 406 (ranked 44th)

Total naval assets: 118; four aircraft carriers

Defense budget: $40.5 billion

4. India

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AP

Power Index rating: 0.1065

Total population: 1,296,834,042

Total military personnel: 3,462,500 (estimated)

Total aircraft strength: 2,082 (ranked 4th out of 137)

Fighter aircraft: 520 (ranked 4th)

Combat tanks: 4,184 (ranked 6th)

Total naval assets: 295; one aircraft carrier

Defense budget: $55.2 billion

3. China

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Reuters/Stringer

Power Index rating: 0.0673

Total population: 1,384,688,986

Total military personnel: 2,693,000 (estimated)

Total aircraft strength: 3,187 (ranked 3rd out of 137)

Fighter aircraft: 1,222 (ranked 2nd)

Combat tanks: 13,050 (ranked 2nd)

Total naval assets: 714; one aircraft carrier

Defense budget: $224 billion

2. Russia

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REUTERS/Mikhail Klimentyev/RIA Novosti/Kremlin

Power Index rating: 0.0639

Total population: 142,122,776

Total military personnel: 3,586,128 (estimated)

Total aircraft strength: 4,078 (ranked 2nd out of 137)

Fighter aircraft: 869 (ranked 3rd)

Combat tanks: 21,932 (ranked 1st)

Total naval assets: 352; one aircraft carrier out of service indefinitely

Defense budget: $44 billion

1. United States

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US Marine Corps photo by Lance Cpl. Kathryn Howard/Released

Power Index rating: (NATO member) 0.0615

Total population: 329,256,465

Total military personnel: 2,141,900 (estimated)

Total aircraft: 13,398 (ranked 1st out of 137)

Fighter aircraft: 2,362 (ranked 1st)

Combat tanks: 6,287 (ranked 3rd)

Total naval assets: 415; 24 aircraft carriers

Defense budget: $716 billion

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