And the British Armed Forces, once the dominant military on the planet, has only six or seven (a couple of speciality sub-ranks in the RAF not-withstanding). Like the USAF, rank progression - particularly in the RN - is strongly tied to training/career development rather than merely time in rank. The Royal Navy uses the following system:
Able Rate 2 (equiv to Ordinary Seaman, roughly NATO E1-2) - Basic rating device only - on entering a sub-branch Able Rate, AB class 2, under training
Able Rate 1 (equiv to Able Seaman, roughly NATO E2-3 rated) - Basic device with star above on qualifying professionally for Able Rate, AB class 1, operationally trained to carry out basic tasks and expected to train for next level as Leading Hand.
Leading Rate/Hand* (equivalent to E4) - Basic device with star above and star below on qualifying professionally for Leading Rate, able to carry complex tasks and lead others and expected to train for next level as Petty Officer.
Petty Officer (equivalent to E5-6) - Basic device with crown above on qualifying professionally for Petty Officer, able to command, instruct others and carry out more complex tasks.
Chief Petty Officer (equivalent to E7+) - Basic device with crown above worn on the on both lapels on number 1 dress and above the left breast pocket on working dress Chief Petty Officers attain no additional professional qualification, able to show advanced leadership, training abilities and perform the most complex tasks.
Warrant Officer 2** (broadly equivalent to E8, but includes elements of WO & CWO) - Trade Brades as per CPO, but with a different insignia.
Warrant Officer 1 (broadly equivalent to E9, but includes elements of senior CWO) - Trade Brades as per CPO, but with a different insignia.
* = in the Army, RM and RAF Regiment, this is split into Lance Corporal and Corporal.
** = No longer appointed in the RN, roughly equivalent to a "First Shirt" in the other services.
Able Rate 2 (equiv to Ordinary Seaman, roughly NATO E1-2) - Basic rating device only - on entering a sub-branch Able Rate, AB class 2, under training
Able Rate 1 (equiv to Able Seaman, roughly NATO E2-3 rated) - Basic device with star above on qualifying professionally for Able Rate, AB class 1, operationally trained to carry out basic tasks and expected to train for next level as Leading Hand.
Leading Rate/Hand* (equivalent to E4) - Basic device with star above and star below on qualifying professionally for Leading Rate, able to carry complex tasks and lead others and expected to train for next level as Petty Officer.
Petty Officer (equivalent to E5-6) - Basic device with crown above on qualifying professionally for Petty Officer, able to command, instruct others and carry out more complex tasks.
Chief Petty Officer (equivalent to E7+) - Basic device with crown above worn on the on both lapels on number 1 dress and above the left breast pocket on working dress Chief Petty Officers attain no additional professional qualification, able to show advanced leadership, training abilities and perform the most complex tasks.
Warrant Officer 2** (broadly equivalent to E8, but includes elements of WO & CWO) - Trade Brades as per CPO, but with a different insignia.
Warrant Officer 1 (broadly equivalent to E9, but includes elements of senior CWO) - Trade Brades as per CPO, but with a different insignia.
* = in the Army, RM and RAF Regiment, this is split into Lance Corporal and Corporal.
** = No longer appointed in the RN, roughly equivalent to a "First Shirt" in the other services.