Yesterday it was in the mid-50s and I figured the ground must be thawed by now. So I grabbed the steel post, step ladder, level, and sledgehammer, and went to work. I lined the post up with the flats on the tip perpendicular to the cedar post, and after a few light hits the head fell off my sledgehammer. The handle rotted away AGAIN. The first time was because it sat in my shed for so many years, and water ran right in whenever it rained. I had it setting on the sole plate instead of the bare concrete most of the time, but it rotted away anyway. I fixed it last year, but not well enough. It still rotted away from setting on the stairs in my damp basement. The plastic wedge broke when I knocked the remaining bit of the handle out, so I pounded in as many 16 penny nails as it would take instead. Most of them went in 1-2", and a few went most of their 3" length. The whole accumulation adds up to a wedge of steel.
Round 2: I went back outside with the newly reassembled sledgehammer and pounded the post in 30" deep. I was going to to stop at 2 feet, but once it got past the concrete or gravel, whatever was around the post, it went in so easily I accidentally went 25", then went another 5" to make sure it was in deep enough. That only left 33" above ground. The fence was leaning away from the post and I had to pull the top in to fasten the 2 together. That fence post just happens to be right across from the corner of my house, where there's a door going down into the basement from the back yard. I didn't want to use the winch on my ATV to pull the fence in, and I don't own a come-along, but I do have some ratchet tie-down straps I use to strap my ATV to the trailer. There's an awning over that 3rd house door with a diagonal 2x4 on each side supporting it. I cut my 15' ratchet straps down to about 5' when I bought them so they're not long enough to drag on the ground. I ratcheted the mechanism on 1 strap to lock it and looped it around the 2x4 supporting the awning. And put the other one around the fence post. When I tried hooking them together they weren't quite long enough, so I locked the ratchet on the strap on the post, hooked onto it with the 3rd strap, hooked the other end on the other strap, pulled the slack out and ratcheted the fence over to the post. I didn't need the 3,500 pound winch with synthetic rope and remote control, a 500 pound tie-down strap worked just fine.
Once everything was n place I cut 3 pieces of pipe strap about 11" long and bent a curve into the middle of each one. Then it was a simple matter of zapping 3, 1 1/4" screws through the end of one strap into the post, wrapping it around the other side and zapping 3 more screws in, then repeating the procedure with the other 2 straps. I filled the pipe from the top to however far down is it went with spray foam, used more spray foam to fill a 24', 15-ounce aluminum T-Ball bat I found next to my car one day, and called it quits. Today I went out with a knife and cleaned up the little bit of excess foam. Then I cut a piece out of the edge of a pill bottle cap because there was no space between the 2 posts to slide it over the pipe. I put a big glob of ALEX PLUS All Purpose Acrylic Latex Caulk Plus Silicone in the bottle cap and smooshed it down on top of the pipe. Now I don't have to worry about the pipe filling up with rain and snow and rusting out too fast. And no wasps or other critters can nest in it either. I had a bolt screwed into the spout of the partly used tube of caulking, with more caulking smeared over the top of it. It was sealed up really well and didn't dry out, so I did the same thing with it today. The covering of caulking stuck to the bolt, leaving the tip of the tube clean, and I scraped that off before I put the bolt back in. I held he sledgehammer with one hand right below the head and one a comfortable distance away, and tapped on the post instead of trying to take a swing at it. Once the pipe was in the ground a certain amount it was easier than driving a nail, except the hammer weighs 16 pounds, plus a half pound of nails, instead of of 16 ounces.

Nailed it!
If anyone is wondering what's up with the downspout, after some @$$hole stepped on it and it folded, I straightened it out by sliding it over one of these steel posts, lying that across my sawhorses and hammering the downspout back into shape. Then I put the broken part in a cast.

I wrapped a whole bunch of 1" wide, O.D. Green duct tape around it. I think I used everything that was left on the roll I got from an army surplus store, and the rest is on my sledgehammer handle where I broke it a long time ago. The duct tape does double-duty as an overstrike protection collar, as well as holding the split together.

There's a carriage bolt in the splash block that keeps the downspout from sliding around, no matter how bad the weather is. The splash block in the front yard has 2 carriage bolts, right in the corners like this one used to, since it's in a straight line with the downspout. I had to take the bolts out of this one, and use one in the left side so it works when it's turned sideways.