With its National Defense Strategy released earlier this year, the US detailed its shift from small-scale operations like counterinsurgency and toward a potential fight with a rival like Russia or China.

Countries around the world have made similar moves, refocusing on large-scale conflict.

Amid those changes, head-to-head comparisons of military strength are hard to come by. Global Firepower's 2018 Military Strength Ranking tries to fill that void by drawing on more than 55 factors to assign a Power Index score to 136 countries — adding Ireland, Montenegro, and Liberia to last year's list.

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 taken into account.

While recognized nuclear powers receive a bonus, 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 there is a lack of diversity in their fleets.

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" for any military 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: