Back to the OP a lot of the conflicts we consider “conventional” really weren’t. For example, was the Korean War a conventional conflict? It was at the start a battle between two regimes claiming to be the only true government; one was the well armed northern regime, the other a poorly armed and led southern regime. That sounds a lot like a civil war that other countries got involved in than a true conventional conflict. Same for the Vietnam War. Yet we consider those conventional conflicts.
Kashmir, Cyprus and Korea are not valid examples. They are pre-existing unified countries that were divided, with lingering hostilities over the terms that arose as a consequence of their civil wars.
In the context of Africa, Chad is a major military power, based on having experienced, disciplined soldiers who know how to fight, are willing to do so, and have enough working motor transport to fight a mobile war. But that battlefield transport is the Toyota Hilux with a heavy machine gun on the back (often the turret off an old soviet armoured car) and they have no meaningful air force unless the french are on hand to help them out.
They spanked the Libyans like a tambourine, and have diced’n’sliced the various ragtag militias and bandits infesting neighbouring countries. But still - the Hiluxes were paid for and supplied by France, and without French air cover/reconnaisance/logistics they would probably be a lot less formidable in combat. So again - ‘foreign friends’ are making all the difference.
Cameroon is also interesting - as I understand it they are a militarily getting a lot of training and support from Chad, who really are becoming quite the major regional player.
Ah, the Toyota War. A lot of them used French MILAN anti-tank missiles on the back during the war when they drove the Libyans out of northern Chad. Wasn’t someone saying something about it being hard to find examples of one country invading its neighbor in the past century?
Thing is, it’s hard in European history to find examples of two countries going at each other, and everyone else staying out. In any war between two parties the neighboring countries have an interest in the outcome, and often provide support for one or more parties in the war. This support can range from sharply worded diplomatic messages to supplying money, or weapons, or troops.
So what the OP is categorizing as a “conventional war”–Country A fights country B, and they fight alone until A or B gives up–is actually a pretty rare sort of war.
In the context of the thread, they mean force-on-force traditional warfare, not some sort of insurgency, civil war or not.
The Korean War was definitely conventional, while Iraq started that way, but ended up as an insurgency. Hence the “Mission Accomplished” stuff- we’d crushed the Iraqis in the conventional part of the war, and the insurgency hadn’t really got rolling yet.
For an older example, the US Civil War was a conventional war, even if it was a civil war at the same time.
Something like say… the ISIS/Syrians/Kurds fighting each other is a lot less like a conventional war than a lot of others; it seems to be a bunch of irregulars and warlords skirmishing from what I can tell, without clear battle lines, etc…
In general, in modern warfare, an all-out no-holds-barred military conflict does not end well for one side. Typically one side out-numbers and out-muscles the other, and especially now, if they get air superiority then they win fairly quickly. With air support and technical superiority, that side can quickly decimate the opposition from the air, isolate armies from supply lines and destroy fuel supplies and ammunition stores.
I suppose the issue with Africa and most global theatres is that there is typically one strong power who can dominate the others; any attempt at full-out war results in that side winning, or it degenerates into a guerilla warfare. Generally those neighbours will avoid getting into a war they cannot win. When they don’t, the shooting is over pretty fast - as with the war that ousted Idi Amin.
(The wars that degenerated to stalemates typically were either guerilla wars like Vietnam or Afghanistan; or they were limited-theatre wars like US vs. North Vietnam, or the Koreas, where the resupply chain itself (Russia, China, USA) was beyond the war zone exempt from direct attack; the exception I think of is Iran-Iraq, where both sides ground each other back to WWI level tech and WWI level trench warfare.
The Iran-Iraq War was fought with relatively state of the art weaponry on both sides; while not bleeding edge technology it was very current for its time. For example Iran had US supplied F-14s (Iran is the only country to have made a kill with an AIM-54 Phoenix), AH-1 Cobras, TOW anti-tank missiles and HAWK SAMs, Iraq had T-72 tanks, Mirage F-1 fighters and Exocet anti-ship missiles. In any modern conventional war that stalemates both sides will naturally dig in to the point of the defenses becoming a trench line, which inevitably invites comparison to WWI. Korea was described this way once the two year long stalemate set in from 1951-53, so was the Eritrean–Ethiopian War from 1998-2000: