Well it depends on how you approach and interpret this question. If you mean powerful by means of mass and size, then hands down it is China, as they are the largest military in the world, topping out over one million personnel. If you are meaning powerful in terms of effectiveness, technology, and size, then I would said it would be the United States. Given our size (I believe total military personnel is at something like 500,000 currently), we are the most effective and technologically advanced military in the world. I am in the Military Police and can tell you that daily we are updating and re-evaluating our tactics and resources. China poses a great threat, however, I believe in a toe-to-toe war we would eventually win. I say this because China is just now starting to multi-train their soldiers. What this means is that they are currently operating on a modified Russian tactic for military training. The Russians would train each soldier on one thing and one thing only. For instance, you might be the radio operator and that is all that you do. You know nothing about deploying grenades or mines or mine detection. Thus, if I wanted to eleminate communications I just need to eleminate you, as you are the only one trained to operate the radio. China does something similar to this. Typically they will train their soldiers in radio operations, mine detection, etc. as well as their specific job (such as tanks, infantry, and the sort). The United States, however, trains our soldiers to be effecient in a little bit of everything. A U.S. soldier can fire a weapon, knows a little about infantry tactics, can detect mines, deploy grenades and mines, operate a radio, etc. What I mean is that the U.S. soldier is not an expert on one thing, but rather is effecient in a multitude of tasks. China is now realizing that to be effective in a toe-to-toe long-standing war, they must begin training in this same fashion.

So, being biast to my own military, I would have to vote that the United States is the most powerful military in the world. I know many people say China simply because they outnumber us in soldiers 10:1, but the number is not what counts. What matters is the effectiveness of your soldier. Our soldiers are trained to do the job of typically three or four soldiers, thus we really have trained our smaller sized military to do the job of a military the size of China, if not bigger.

Personally, I think it would be a very difficult war to win against China, although I think we would succeed. Let's just hope we never have to find out. I hope this answers your question!

Germany wins, They got Nazi Zombies
LOL jk.

UK has the best special forces but US prob has the best overall military especially with that rail gun they were showing off the other week o.o

In terms of statistics, China has the biggest military out of all of those.