BhanupriyaN
Please help me understand why E is incorrect
First let's breakdown the argument:
Ironically, soldiers in the military often find themselves at risk of losing their specialist roles as they gain experience and are moved to more administrative desk duties. Many specialists undertake a voluntary rank reduction to hold on to roles such as flying, tasks that they are passionate for. (all background - specialists choose to stay in lower rank positions)
The higher ranks of the military, therefore, are filled with people who are career-climbers. (claim that those who take the higher ranks are career-climbers, not specialists)
According to some analysts, this imbalance contributes to the poor planning of many military operations in recent years. (Conclusion: having non-specialists in high ranks contributes to poor planning).
So let's look at (E).
(E) Whether poor planning is more often due to lack of field data or intelligence than to the planning skills of high-ranking officers.
For evaluate questions, you should be asking how the answer to the question posed in the answer choice impacts the argument. Here, what if poor planning IS more often due to lack of field data/intelligence than to the planning skills? What if it isn't? So let's say, of the 100 instances of "poor planning" 60 are because of lack of data/intelligence and only 40 are due to planning skills? Does that negate the fact that the planning skills of "career climbers" isn't
contributing to poor planning? What about if the balance was 90/10 - that 10% is still
contributing. The argument doesn't claim that all poor planning in military operations is caused by the imbalance, so we don't need to defend imbalance against other possible causes of poor planning.
Let's try with a simpler example: a
local restaurant recently replaced all of its experienced waitstaff with brand new hires who have never waited tabled before. According to many regular customers, this decision is a contributing factor to the poor service that they've received when eating there.
What would you want to know? Would you want to know whether the customers were getting better service when the experienced staff were there (a direct comparison of experienced vs inexperienced), or would you want to know how frequently having a really busy night with an excessive number of customers contributed to poor service? If you're blaming expertise for the entire problem, then you'd want to know about confounding factors. But since you're just saying that the swap contributed, they you only want to evaluate whether the swap actually did do anything at all, so you need to compare the customer service when it was experienced vs non-experienced staff. So then let's return to (A).
(A) Whether military operations planned by specialists who retained their field roles tend to be more successful than those planned by career-climbers in higher ranks.
This is exactly the comparison we need. If you want to say that not having specialists has any contributing blame at all, you have to show whether there really is a difference when operations are planned by specialists vs when they're planned by career-climbers. This is the same as the restaurant analogy. If you want to blame any of the problem on new and inexperienced staff, you'd better show me evidence that there is actually a difference in service between these two groups.
Hope this helps!

Whit