I encourage you to read all of Nehemiah 4 to get the full context and find other jewels of spiritual wisdom, but look at verses 17-20.
Sword on the hip, a weapon in one hand and working to rebuild with the other hand, all the while under enemy threat. If you remove the swords and weapons the enemy could have overtaken them, no matter what kind of walls they built, if they could complete them at all. If overtaken, they would be working with both hands, under tyrannical rule. Interesting.
Also interesting is 19 and 20 where it basically for concentration of defense by the sounding of the trump. Even with weapons, if you remove the trump of guidance and direction, they probably would still be overtaken.
Most important of all is to remember that Weapons and Trumps are useless without God, for "our God shall fight for us".
-Pastor Jesse Rowland
Nehemiah 4:17 They which builded on the wall, and they that bare burdens, with those that laded, every one with one of his hands wrought in the work, and with the other hand held a weapon. 18 For the builders, every one had his sword girded by his side, and so builded. And he that sounded the trumpet was by me. 19 And I said unto the nobles, and to the rulers, and to the rest of the people, The work is great and large, and we are separated upon the wall, one far from another. 20 In what place therefore ye hear the sound of the trumpet, resort ye thither unto us: our God shall fight for us.