Whatever happens, happens by his will". Porter is using the fact that at the toughest of times, even the least religious of people turn to God to try and make sense of what has happened, or try to find someone to blame.
When porter starts making a list of people and creatures that aren't allowed to be taken into the bomb shelter is when the severity of the situation starts to sink in. "Do not take birds the old bed ridden", we are told they will "consume fresh air" and that "you can do nothing for them". By this point, the reader realizes that there is something very wrong if people and animals are being left to die.
During points in the poem, certain words are repeated, "turn off your television now. Turn off your radio immediately the services end". By using repetition, the voice of the poem is drumming into the readers brain exactly what they should be doing.
At this point in the poem we find out that people have known about the bombs coming for a while. We find out that people have been preparing for a while. We find out that they have all types of medication ready in waiting for this "pills marked one and two Red pocket in No. 1 survival kit". There are death capsules in the kit called "Valley Forge", by using a light-hearted name, it makes death sound like no big deal.
By using harsh words like "instructed", Porter get his point across easier about how worried everyone really must feel. The last few lines of the poem are a lot more decisive, and more like facts. The truth becomes a lot more blunt even though it is still being sugarcoated to some extent, and is still trying to look on the bright side. "Some of us may die not likely to be you the sun is shining, death is the least we have to fear what ever happens, happens". The voice of the poem is trying to build up confidence.
The very last line is an order. "Now quickly to your shelters". This is the most forceful line in the whole poem.