GMing a city defense

[guncrazy]

The game commenced last night (Tuesdays are game night) So far the battle has started off poorly for our struggling PCs. After some time preparing and talking amongst themselves about defense prep they get underway and fast forward to the action. The siege begins with M198's shelling the town killing 10 men and giving one of the PCs a wake up call lol. Due to a great observation roll on the outskirts one player spots their F.O in the distance (we are in Texas/NM so desert terrain. The 81mm mortar is ordered to fire on that position. The player rolls for the mortar team and rolls a 20, catastrophic failure! being the nice GM I am I let him roll again to avoid a true nightmare scenario, the player rolls another 20. The round cooks off in the tube killing the crew and all remaining round for the one mortar. Only 1 81mm remains in the city. Round 2 sees the second mortar roll a 1 on its roll and hits the F.O position silencing the militias Howitzers, at least for the time being. Trucks can be seen and heard approaching the city as the shaken but determined defense prepares for urban combat....Thats where it stands now, next round will be actual initiative and combat commences.