This is the line that has the left convinced that Obama won the debate with Romney on Foreign Policy.
Note that the two examples Obama uses immediately following his bayonets and horses line were aircraft carriers and submarines--navy vessels. He says they can do more than they used to, which is true, but it is also true of our enemies. So if Romney is correct and our overal naval forces are too depleted, you can actually encourage your enemies to catch up with you if you indicate they have a chance to do so. If you have overwhelming dominance, they won't bother.
All-in-all, I think the left is engaged in wishful thinking as to the debate last night. Obama got his zingers in, but Romney appeared poised, educated, plausible and most of all, optimistic.