The FBU said firefighters were climbing hills in unsuitable boots and non-breathable layers intended for house fires, because they did not have enough appropriate kit.
Sean Cayford, a firefighter in Bridgend, said crews were told in mid-August that there were no pumps or fire appliances available across the entire brigade's region. "I've never heard that before," he said. On one day, he could see six or seven of the most serious category of wildfires on the horizon from Tredegar mountain. Even with help from brigades across the UK, they did not have enough firefighters. He said injuries were common and many colleagues were still unable to work.
Gemma Thomas, a control room worker, said the average call volume is 200 to 300, but on their busiest day this summer they had almost 2,000. "It was just relentless," she said. Staff were so exhausted they had to take breaks one at a time for just ten minutes. She wants to see an increase in firefighter numbers.
Gareth Tovey, executive council member for Wales, said there was poor preparation and that at some stages there was zero crew back-up for vast parts of south Wales. The FBU says there is a shortfall of 400 firefighters in Wales and that the union had been warning for years about the need for action. He said bringing in the army is "not a silver bullet".
The Welsh government said it does not provide core funding for fire services, but "recognise the concerns raised and are clear that we need to do all we can to reduce the risk of wildfires". It said individual fire and rescue authorities determine their own budgets and should take the summer's fires into account.
First Minister Rhun ap Iorwerth is hosting a climate change and resilience summit in Merthyr Tydfil on Thursday. He said this summer's fires were "much more dangerous than fires in other years" and that the aim is to take practical steps to reduce the risk of wildfire and ensure a swift response.
North Wales Fire and Rescue Service is applying to the Welsh government's emergency assistance scheme to cover an additional £500,000 the wildfires cost. At one point, firefighters in north Wales were managing six wildfires at once, more than ever before.
A report from the UK's Environment, Food and Rural Affairs Committee said the wildfires exposed weaknesses in the UK's resilience and preparation, and called for a national wildfire prevention campaign and wildfire risk indicators in weather forecasts.
South Wales Fire and Rescue Service said it is proud of the response and recognises that climate change requires it to adapt and strengthen its ability to respond. It is engaging with unions about the investment needed.