Why is Certainty to be Expressed by the Present Subjunctive?

Question

In North & Hillard Ex. 209 the following is to be translated into Latin:

The general delivered this speech before his men: "You see how great the forces of the enemy are, and how impregnable their position is. If we attack them we shall without doubt suffer a severe defeat."

The Answer Book:

imperator ita apud suos contionatus est: "videtis, milites, quantae sint hostium copiae et quam inexpugnabilem locum teneant. si eos statim adoriemur, sine dubio magnam cladem accipiemus."

In the English version the general is certain about the size of the enemy forces, and how impregnable their position is. In the Latin, the indefinite article, the present-subjunctive verbs "sint" & "teneant".

To determine what this is, I eliminated what it isn't. My first thought was "subordinate clause" usually found in indirect speech; but, "forces" & "impregnable position" are of equal merit: in the general's mind/ statement the one is not subordinate to the other. (I considered "indirect question" but the general is telling his men--you see [you can see that...]; there is no interrogative word.) Is the general expressing a subjective opinion? No, the implication is that he can see the "forces" & "their impregnable position"; he is stating facts.

The remaining uses-of-the-subjunctive e.g. purpose (final)/ result (consecutive) "ut"-type clauses through to concessive clauses in which, the latter, the general's certainty would require all the verbs to be indicative, do not apply.

In direct speech, when the speaker is certain about everything, and there are no special grammatical circumstances, why is the present subjunctive deployed?

A secondary point:

in "how great the forces of the enemy are", "how" is understood. In "how impregnable their position is", "how" is given as "quam". Why isn't "quam" written before the former, then it applies to both. Alternatively, "quam" is omitted and "how" is understood for both concepts--both or neither?

Answer 1

It is an indirect question. The question words are quantae and quam.

The direct version would be:

How great are the forces of the enemy, and how impregnable is their position?

Quantae sunt hostium copiae et quam inexpugnabilem locum tenent?

Indirect questions always get the subjunctive (conjunctive), no matter how certain the matter is.

The Latin for "how large" is quantus, whereas "how" alone is quam — roughly. Thus you can't have the same quam for both questions in Latin. And even if you could, I think the sentence flows better with repeated question words.