What... what the...?

Hello everybody.

Next was Mizutani’s turn, but slipping and sliding, he was no match

for their friend either. Kitami said, “Good. Now I’ll have my revenge!”

He spit on his hands and stepped up, but Uragawa was undaunted.

Kitami planted his legs and pushed and heaved with so much effort that

his face turned red, but eventually he was pushed back.

“What…what the…”

At this, Kitami redoubled his efforts and pushed for dear life, but

slipping centimeter by centimeter, he was forced back, and finally,

saying “What… what the…” all the way, he was defeated.

The boys are playing pole-pushing, a game in which each player takes one end of a long stick and tries to push the other player back.

Now would you please tell me what “What…what the…” means?

And also I can't figure out the second bold part, pushed for dear life, but

slipping centimeter by centimeter?

Does it mean Kitami was slipping each centimeter he was trying to push?

Thanks so much for the help ????