In a couple of my campaigns the option to declare war against a nation desappears after a period and after. Is it a bug or a feature? (eg you cannot declare war against a nation to whome your attitude is high)

<t> I searched the forum for draft rules but did not get an answer about the draft pool.<br/>
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Well every month every supplied unit which is depleted might get reinforced from the men in the draft pool. Lets say a total sum of 10.000 men will be detached to various units and 500 will be ...