could any of the kingdoms at middle earth attack the southern continents?

[Zigûr]

Are we talking about Harad here? Which, incidentally, is actually still part of "Middle-earth." I assumed originally that this thread was specifically talking about the "Dark Land", which is to say the far Southern continent which appears on one of the 1930s Ambarkanta maps of Arda and might potentially be considered a quasi-Australian or Antarctican landmass. This is to say, a region about which we know literally nothing apart from a shape and two names, "Dark Land" and "South Land", the former of which can easily be confused with Mordor and the latter with Harad.

news would have spreaded from the haradrim and corsairs

Given that "Harad" is just a catch-all name for almost everything South of Gondor, aren't all the inhabitants of the "Southern Continent" technically Haradrim? If we're not talking about the "Dark Land," isn't the "Southern Continent" just Harad?
It's been stated that there was probably conflict between the Easterlings and the Haradrim and we know for a fact that Gondor and Rohan were forced to attack certain parts of Harad (and Rhûn) in the Fourth Age to defeat realms which refused to put aside their ancient enmity with the West even after the fall of Sauron. So if by "Middle-earth" we mean "parts of Middle-earth north of Harad" then yes they did, which must as such prove that yes, they could.

[tom the eldest]

Nah ,harad not included in the middle earth category.
Now,gondor did manage to push the southrons way to their homeland but they never go as far as far harad and the southern continent.if gondor can invade to the south,why they not push their advantage and invade the dark lands?the possibility is,a very large mumakil troops await them in far harad,and the gondorians then too afraid to attack them,knowing the risk.then they retreat.

[Morthoron]

Originally Posted by tom the eldest

Nah ,harad not included in the middle earth category.
Now,gondor did manage to push the southrons way to their homeland but they never go as far as far harad and the southern continent.if gondor can invade to the south,why they not push their advantage and invade the dark lands?the possibility is,a very large mumakil troops await them in far harad,and the gondorians then too afraid to attack them,knowing the risk.then they retreat.

I suppose if we were playing with toy soldiers on a game board, that would be the case. Did it occur to you that there was simply nothing worthwhile Gondor wanted further south? They got what they required in Umbar and Near Harad, and nothing more interested them. There is nothing to support what you are saying in the text.

[Zigûr]

Originally Posted by tom the eldest

Nah ,harad not included in the middle earth category.

For the purposes of this discussion, or in general? Because Harad is definitely part of Middle-earth in the books.

Originally Posted by Morthoron

Did it occur to you that there was simply nothing worthwhile Gondor wanted further south? They got what they required in Umbar and Near Harad, and nothing more interested them. There is nothing to support what you are saying in the text.

Exactly. Given how little we know about Far Harad, it's virtually impossible to speculate. Besides, conquering a little of Near Harad doesn't mean Gondor had the strength to conquer what might have been equivalent to, for all intents and purposes, the whole of Africa, even if they wanted to.
That being said I think the usefulness of elephant cavalry ought not to be overstated as well. As formidable as the Mûmakil were compared to their later descendants, they were not invincible, and elephants make for temperamental and inefficient beasts of war.

Originally Posted by tom the eldest

if gondor can invade to the south,why they not push their advantage and invade the dark lands?

For what purpose? This is treating the situation like a game. It may be fiction, but it also adheres somewhat to the rules of history. Even within the bounds of Tolkien's narrative the Men of Gondor do not appear to have fought wars "for fun" or without reason.

[Belegorn]

It appears to me that the rise of the power of Númenor did coincide with their imperialism, their quest for domination. I think that perhaps they may have expanded had not they took such a big hit in the downfall of Númenor and the huge fleet that sailed to Aman. That's the loss of a lot of manpower. However, these were basically the Kings Men who were more of the conquering type than with the Faithful which is probably why even when Gondor became like Númenor in Middle-earth when its power waxed they were not pushing south or east, except of course the Ship-kings who took Umbar, and "the kings of Harad did homage to Gondor, and their sons lived as hostages in the court of its King." [Appendix A]

"their own land seemed to them shrunken, and they had no rest or content therein, and they desired now wealth and dominion in Middle-earth... Great harbours and strong towers they made, and there many of them took up their abode; but they appeared now rather as lords and masters and gatherers of tribute than as helpers and teachers." [Sil., Akallabêth, p. 329]

In this quote were are told how before they were helpers, where they instructed Men how to grow and build things and were seen as gods. Although in Unfinished Tales it is said how when they first returned around 2nd Age 600 the Middle Men did see that they shared a kinship with the High Men.

Originally Posted by Zigûr

For what purpose? This is treating the situation like a game.

Erendis spoke of the Men of Númenor:

"Anger they show only when they become aware, suddenly, that there are other wills in the world besides their own. They will be as ruthless as the seawind if anything dare to withstand them... Númenor was to be a rest after war. But if they weary of rest and the plays of peace, soon they will go back to their great play, manslaying and war." [Aldarion and Erendis, Part 2, ch. 2, p. 216-217]

It appears, at least in her view, that the Men of Númenor do hold it in some degree as sport, or a game. There has been mention of warlike lines among the nobles where it concerns the High Men.

[Alfirin]

Such is the way of the mighty of men, There are always those who will wrap themselves in metaphorical Gulon fur, who no matter how much they have, want more forever. And regretabbly, those kind of people often get great power, by getting the similary avaricios to join them. Remember what was supposedly written on Alexander the Great's tomb "Now this mound is big enough for he for whom the whole world was not."

[Nerwen]

But Belegorn and Alfirin, the question being posed is (as far as I can work out, anyway), "why didn't Gondor just go ahead and take over the entire known world?". And possibly more than that, since tom talks about "the southern continent". That, I believe, is the sense in which "treating it like a game" is meant- the OP seems to take it as a given that world domination (more-or-less) is everyone's sole objective, regardless of practicalities.

[Inziladun]

Originally Posted by Nerwen

That, I believe, is the sense in which "treating it like a game" is meant- the OP seems to take it as a given that world domination (more-or-less) is everyone's sole objective, regardless of practicalities.

Regardless of feasibility, as well. Gondor was quite incapable of launching an offensive against Rhûn or Harad with the aim of empire. As was seen, it was all Gondor could do to defend themselves from attacks by those enemies.

[Belegorn]

Originally Posted by Nerwen

But Belegorn and Alfirin, the question being posed is (as far as I can work out, anyway), "why didn't Gondor just go ahead and take over the entire known world?". And possibly more than that, since tom talks about "the southern continent".

I think it was probably a question of manpower as I mentioned in my last post. I believe Ar-Pharazôn took offense to Sauron claiming to be King of the World or some such. Númenor lost a lot of men in its downfall, even the King and his wife. The Dúnedain were few after Númenor's destruction even though there were settlements in M-E before its destruction.

"On the western shores in the days of their power the Númenóreans had maintained many forts and havens for the help of their ships in their great voyages; and the chief of these had been at Pelargir at the mouths of the Anduin in the land that was after called Gondor... Now the people of Elendil were not many, for only a few great ships had escaped the Downfall. There were, it is true, many dwellers upon the west-shores who came in part of the blood of Westernesse, being descended from mariners and wardens of forts set there in the Dark Years; yet all told the Dúnedain were only a small people in the midst of lesser Men." [RotK; ll. The Appendix on Languages]

Númenor's armies were indeed powerful, they being a powerful people in themselves probably playing no small part. Ar-Pharazôn's "armada that took haven at Umbar was so great, and the Númenóreans at their height so terrible and resplendent, that Sauron's servants deserted him." [Letter# 156] I think it is very possible they could have expanded into other realms had they remained intact as a people.

I do not think great casualties are often necessary in these battles. Turenne often won without really fighting based on his marches and positioning. Perhaps, as happened with Sauron's forces, their enemies would lay down their arms.

Originally Posted by tom the eldest

so the only way the gondorians are able to invade the land is by sea

If they had to invade by sea this would not be a problem as they were a maritime power and great sailors and builders of boats.