According to the index created by Global Firepower (GFP), the top 10 countries by military power in 2018 are:

1. United States of America (USA).
2. Russia.
3. China.
4. India.
5. France.
6. United Kingdom (UK).
7. South Korea.
8. Japan.
9. Turkey.
10. Germany.

With due deference to current circumstances it is interesting to note that North Korea is positioned at number 18.

For 2018 there are a total of 136 countries in the GFP database, with three new countries added this year: Ireland (116); Montenegro (121); and Liberia (135).

Reference

GFP (Global Firepower) (2018) 2018 Military Strength Ranking. Available from World Wide Web: https://www.globalfirepower.com/countries-listing.asp. [Accessed: 02 May, 2018].