And what are defensive skills other than calculating tactics...
Can you really become a class A player by studying tactics?

Ok, some little tips like counter pressure and how / which files you open. Trade off attackers and stuff like that.
But the essence of defense, so to speak, is calculation.
And I'm talking about legitimate attacks. Letting your opponent build up a winning attack and then executing you I file under lack of strategic understanding.

of course you are entitled to your opinion!but you just indirecly acknowledged the huge importance of strategic understanding!great!

I can tell you from experience, it's an absolute fact that all you need to study is tactics. I went from a little over 1000 USCF to 1600 on tactics alone, and I will break into the A-class (or near it) in my next tournament. You might FEEL as though studying those positions help you, and maybe they do to some inefficaciously minimal extent, but they don't move you toward A-class as tactics do.
It's like Michael De La Maza said, class play is almost always decided by tactics. I'll take it further: all class play is decided by basic tactics, whether executed or missed. I love only having played the game for a few years and smashing thes players who have spent thousands of ours on positions, master gams, and openings. If you can't gain 200+ points in a year while being a class player, you haven't caught on. TACTICS.
This is the comment that reignited this thread.
Milliern's current USCF rating is 1569. I don't know why he thinks he will break 1800 in his next tournament. He has won precisely 2 games out of 41 tries against players rated +1800.
In order to become an A player, you must know endgames. Tactics are crucial, but not the whole story.
As a guy who has spent 30 years mostly as an A-player (with a few forays above):
a) A-players all have an opening repertoire. If you don't study openings at least a little you will get rolled up by things like the Danish Gambit and the Fried Liver. Nobody short of Fritz is good enough to figure out all the tactics at the board that many A players know.
b) You have to know some basic endgame play or you will be halving points all the time that simple endgame prep will help you win.
c) Bad startegy can obviously doom you in the A and B class where there are plenty of players who have insight into what kinds of moves are best. You still might win with tactics but the odds are with your strategically prepared opponent.
d) Taking advice from a 1569 player on how to become an A-player is a really excellent idea. I am currently working on a book called "A Study Plan for your Grandmaster title" that I am hoping to make good money on.

John Coffey says this, "Absolutely".
He also says, "There are other parts of the game that players need to study, but for almost everybody below 1800, tactics is their biggest weakness and the easiest thing to improve!"
He goes on to say, "I think that it is important to study tactics every day. The only exception to this might be the days where you play 3 hours or more of speed chess, because speed chess challenges us to think tactically."
Do you agree?
I'm not so sure if I do. Don't Class A players also need to know a lot about chess strategy?
The entire article can be found here: http://www.entertainmentjourney.com/tactics.htm
As a class A player, I got there by studying the middle and end game. Openings and tactics i dont study, as they bore me to tears. I am currently forcing myself to study tactics, and it is getting more tolerable.
The comment i get most from players rated 1900 and above is "You blunted every attack i tried" Does this mean i always know what i did? Nope...not even close. But it apparently is working, whatever it is im doing. Actually i just play simple, sound chess. If i run across an opening i dont know (which is often) I follow the opening principles.
I just need to get to a a playable middlegame. It is there in a usually closed/cramped position i will find an exchange sacrifice. Yes people....tactics do exist in those boring/closed/semi-closed/cramped positions.

The snake oil that de la Maza is selling is potent stuff. Chess really is mostly tactics, as we know from seeing how engines play. His recommendations are actually pretty good, and not at all revolutionary. It's his claims for how efficacious his particular brand is that's off-putting. Every chess coach knows that tactics are important. But you gotta eat your veggies too. You gotta learn basic endgames and openings.
The thing with saying you have to learn tactics is that it's possible to argue that openings and endgames are also all about tactics. This is true, as engines have shown. But humans learn these elements not by studying tactics but by learning general principles.
Learn the general principles behind the endgames, study pawn endings to improve your calculating skills, and work on the basics of development. If you can get those things going along with improving your tactics, you're on your way. It's a bit aristotelian, but try to be good at all facets of the game, don't focus on one to the detriment of other areas.

I was thinking of that when I wrote it, OT! I heard that from my teachers at school in England about a decade before The Wall came out!
I made it to 1860 from like mid 1000 in a year and a couple months with tactics and grandmaster games
Class A really isn't impressive to make it to. But there's a huge theory knowledge difference in class A vs B. I know very little fhess theory and sometimes get destroyed because of it
Also knowing the type of positions you like to play and knowing how to get there helps save lots of time on the clock
My end game skills need work though I'm probably a class D player at endgames and will only play an endgame if I'm absolutely sure it's winning for me

I was thinking of that when I wrote it, OT! I heard that from my teachers at school in England about a decade before The Wall came out!
Some of the best work of Monty Python and Pink Floyd stem from the UK's educational system.
"Breathe deep, the gathering gloom..."

I made it to 1860 from like mid 1000 in a year and a couple months with tactics and grandmaster games
...
1860... USCF?

When people speak of their ratings they really should specify if they refer to OTB ( fide or uscf ) or online ratings . Ofcourse OTB ratings always get more respect/recognition than online ratings , as they should .

When people speak of their ratings they really should specify if they refer to OTB ( fide or uscf ) or online ratings . Ofcourse OTB ratings always get more respect/recognition than online ratings , as they should .
And (well... usually) when people say "help me get to _____ rating" they're not talking about a rating you get from a website.

One would think that if a person made it Class A on tactics, their tactics rating here would be higher than 1284 (42.9% solve rate after 63 puzzles), even if they only spent .3 hours on it.

Wait, no, listen.
You- you didn't let me finish.
I played an 1800 player once, and after 15 moves the position was equal, so I knew I was about 1800 myself.

Wait, no, listen.
You- you didn't let me finish.
I played an 1800 player once, and after 15 moves the position was equal, so I knew I was about 1800 myself.
I can play 15 moves of theory with a 2700 GM and may have an equal position with him at move 15 but it certainly doesnt mean I am also about 2700 strength ! If you play 10 games against A class players and score 50% , or better , then you are likely A class strength yourself .

One would think that if a person made it Class A on tactics, their tactics rating here would be higher than 1284 (42.9% solve rate after 63 puzzles), even if they only spent .3 hours on it.
I think it depends. Its an online account, and maybe someone else was using it? Maybe the users baby tapped the keyboard? Or the cat walked across the keyboard. Lots of possibilities, and yes, they may just not be honest.
IMO the single one department that players below 1800 are truly markedly weak is defensive skills..