Midrash for Sanhedrin 40:5
<big><strong>גמ׳</strong></big> תנינא חדא זימנא אין מוציאין למלחמת הרשות אלא ע"פ ב"ד של שבעים ואחד איידי דתנא כל מילי דמלך תנא נמי מוציאין למלחמת הרשות
it is sufficient to set it up [on one side only].<span class="x" onmousemove="('comment',' Because if actually lowered, it may appear to be standing in its usual position, since then the poles protrude upwards. ');"><sup>6</sup></span> <b><i>MISHNAH</i></b>. HE [THE KING] MAY LEAD FORTH [THE HOST] TO A VOLUNTARY WAR<span class="x" onmousemove="('comment',' In contradistinction to the obligatory war, which was directed against the seven nations that inhabited Canaan. Obligatory war includes also the campaign against Amalek or against an enemy attacking Israel. Voluntary war is waged merely with the object of extending territory. It might therefore be defined as a war of aggression, as opposed to a defensive war. V. Sot. 44b; Maim. Yad, Melakim 5, 1. ');"><sup>7</sup></span>