Something I have wondered about recently, since the advent of ICBM's what is the point of long range bombers like the B2? I understand they have longer range and can carry more payload but wouldn't they be easy prey for fighter jets or SAM's? Surely missiles are a much more attractive option. I don't get why the effort and expense goes into bombers?
Once you launch an ICBM, you're pretty much committed. Even if there is a self-destruct on the missile (I don't know, nor am I making that claim. Additionally, I think debris from such an act would be a big concern.). A bomber also allows you to send something part of the way, and rattle your sabers in the face of the other party without again having committed to the act of the warhead being launched. You can always recall a bomber without having to worry about a debris field or other unintended consequences.
As to the claim that bombers are particularly vulnerable, there are numerous ways they get around this. For instance the B-2 employs stealth to get around this. The B-52 can use standoff weapons to reach out to a target (such as cruise missiles or JASM). Also, the B-52 can use low altitude routes to avoid radar and detection (if you’ve never seen a B-52 do a low level, I recommend you find a route and observe, it’s something else). And on top of all that, the aircraft have defensive systems to help them on their missions (chaff, flares, RW gear, etc.).
Also, with a bomber, you can employ different types of weapons that give you a broader range of response options. You can use bombs of anywhere from a 250lb laser/GPS guided bomb to something much larger. These delivery mechanisms are generally much more accurate than a TBM (Theatre Ballistic Missile) or even an ICBM (InterContinental Ballistic Missile). Those systems are generally inertially guided (some have GPS capability), which can lead to a larger CEP (circular error of probability), meaning that it may not hit exactly where you aim. Those systems rely on a much larger warhead to get the job done than bombs from a bomber. You don't use a Nuke to swat a mosquito, as a bit of military wisdom goes. And, even ballistic missiles can be intercepted by systems such as the Patriot, so they are not a panacea against being stopped.
It's about cost, precision, load, time to target, and risk of nuclear war:
- Cost: ICBMs are very expensive, even compared to a B2 bomber as a B2 can be reused over and over
- Precision: 100 meters or so may not make much difference with a 500 kiloton nuke, but with a 500 pound bomb it's the difference between a hit and a miss
- Load: an ICBM doesn't have that much lifting capacity, they are designed to carry nuclear weapons which aren't particularly heavy. A B2 can carry up to about 40,000lbs of payload and a variety of conventional bombs at the same time, that's much more than the heftiest ICBM
- Time to target: an ICBM's suborbital path takes at least 15 minutes from launch to target, and that's once you get authorization and build a targeting package for it, which all takes time. A great deal can happen on the battlefield in just 15 minutes, so conventional ICBMs only make sense against strategic targets which won't move, and where time is not a factor. A bomber can loiter on site for hours waiting for targets of opportunity to present themselves, or provide air support for troops on the ground. Long-range missiles are no good for that
- Risk of nuclear war: ICBMs were designed for one purpose - nuclear exchange. Several nations have entire defense establishments for the purpose of tracking ICBM launches and responding to them. These nations would need to be notified of a conventional ICBM launch so that they don't react by launching their own nukes. Plus, what if their notification system doesn't work and not everyone gets the message? You'd need an extremely good reason why you would want to risk that!
That doesn't mean that conventional ICBMs don't exist, they may have been developed by now in the Prompt Global Strike program in the US. This uses existing launchers but replaces their nuclear payloads, which is relatively low-cost as the launchers have been developed and tested. It may be a useful capability but it would be unlikely to be ever used due to the risks involved.
Short Answer: Because not every war or military mission needs an ICBM
On the practical level, some air forces still use bombers because large payloads of standoff weapons like air launched cruise missiles are a desirable military option.
Your question assumes a single form of military action: a nuclear attack delivered by either an ICBM or a bomber. It's not an Either / Or proposition.
There is a whole lot more to the use of military force, and the threat of using military force, than that simple binary condition. To ask that question is to fundamentally misunderstand the purpose behind both a bomber and an ICBM. The ICBM and the bomber fulfill two distinct military requirements. Military options are exercised by national political leaders, and national leaders always want options. An ICBM option menu is "nuclear war or not." Bombers provide a lot more options.
All an ICBM can to is make a nuclear attack. That's it. (Its deterrent role is a different matter, but any competent military force provides a form of deterrence ...)
Bombers are multi-purpose war planes. They can carry bombs for a nuclear strike, but they can also carry bombs (or other payloads) for a host of other missions.
The classic example is the B-52. A squadron of B-52's could be on alert during the Cold War, armed with nukes that could be used (but thankfully never were). At the same time, B-52's form other squadrons were in Viet Nam dropping conventional bombs in a war that was not nuclear.
The B-2 likewise has already been deployed to make conventional attacks, but it could (if need be) make a nuclear attack. In that case, however, ICBM's are either already in play or are likely to come into play once the nuclear weapons are used. It's a huge risk and I hope it never comes to that.
A third example are the Russian Bear (TU-95) and Badger(Tu-16) bombers that were deployed a lot by the USSR during the Cold War. They were generally equipped to launch cruise missiles, not bombs, and could carry quite a few of those missiles. That weapons load takes the problem of fighter screen penetration and SAMs out of the picture and makes forces the opposing forces deal with a saturation raid of air -to-surface missiles. (That particular problem is why the USN developed the AEGIS radar/weapons system). The USAF also developed a family of long range cruise missiles that do something similar, and which are deployed on bombers.
Bombers are used much less then they used to be in the piston era. But ICBMs are not the replacement except in nuclear deterrent role. ICBMs are for nuclear attacks only (as already explained in the other answers). In most other roles bombers are replaced by:
- Fighters/attack aircraft. A flight of smaller aircraft can do same or more damage than a large one and they have more options evading or even defending against various threats.
- Cruise missiles. They are not any faster than fighter, but flying 100 ft above ground level they are extremely difficult to detect and intercept.
- UAVs. While they are no match for a fighter and don't have as large payload, they can also fly very low to avoid detection, some are additionally stealth and it's less of a problem if one is lost.
Where bombers are still useful and will likely remain is surprise long-range missions. Bombers can strike almost anywhere in the world from their home base with some aerial refueling. That can be prepared quickly and without having to move many units to forward bases which could warn the enemy. While fighters are also capable of in-flight refueling, they would need to refuel more often and they have no provision for crew rest. B-2 missions often take 30-40 hours.
Bombers are one of the cornerstones of the Nuclear Triad. Along with Intercontinental Ballistic Missiles and Sumarine launched nuclear weapons, nuclear bombers provide the Nuclear Triad with three levels of redundancy, preventing a total disablement of our nuclear strike capability and ensuring a nuclear retaliatory capability for mutual assured destruction in the event of an nuclear attack on the United States.
Lots of other good answers here, but in the interest of getting a bit more global:
Let's say you're Angola and you're trying to set up your own air force after gaining independence from Portugal in 1975.
Is anyone going to sell you some ICBMs? Yeah, someone might, I guess. But you should probably keep shopping around.
Eventually you get the Soviets to sell you some fighter/bomber Fitters in 1982. Later on you buy more from Belarus and then Slovakia.
You use them in a couple of civil wars, which is the sort of role that ICBMs are not really well-suited to.
Where the B-2 is concerned, one must first look at the original contract, calling for 132 aircraft. Relevant as, not unlike our current Ohio and Virginia Class submarine force - the B-2 proposal approved and signed by Jimmy Carter outlined - among other things at any given time fifteen B-2 would be airborne. This deployment - in and of itself the proverbial "Game Changer" - was to be in place seven days per week, 365 days per year, 24 hours a day. As for the other bombers mentioned in this thread, understand that the B-52 cannot - and never has been able to - launch with a full payload of ordinance AND a full complement of fuel - Its one or the other, the political fact that taxpayer funds have been wasted on upgrades for this old dog for decades notwithstanding. Further, understand that after receiving his B-2 briefing and consulting with Joint Chiefs, Mr. Carter cancelled the dog known as the B-1 Lancer in order to go forward with full program development and production of the B-2. Like the B-52, the Lancer is incapable of launch with a full ordinance payload coupled with a full load of fuel; both need refueling not long after takeoff should the sortie require it. With the incomparable range of the B-2 lifting body design - it can circumnavigate the planet with but two refueling's - its incredible air-frame strength, making it our only bomber capable of takeoff with both a belly full ordinance and a full load of fuel, and the current lethality of 21st century JDAMs coupled with the new GBU-39 - of which the B-2 can carry 88 - the other aircraft in the U.S. inventory aren't in the same ballpark. Heck, it isn't even the same sport!
Aside from the cost, there is no way to tell if an ICBM is carrying a nuclear warhead or a conventional warhead. It would be very easy to spook a major power into misinterpreting intentions if a nation goes firing off a bunch of ICBM's.
We call China up and say that all those ICBM's we just shot off aren't carrying nukes, and are aimed at N Korea and not you... I don't think they'd take that explanation at face value. I wouldn't.
Really, not a smart thing to do. The consequences of misunderstandings could be severe.
Cruise missiles, such as the Tomahawk, have been used in very high risk situations where a downed aircraft and a captured pilot would be politically costly. However, cruise missiles can't deal very well with changing situations.
A cruise missile can't tell if civilians have drifted into the target area, and abort the mission or choose another target. A pilot in an aircraft with eyes on target can.
It appears likely that larger remotely controlled drones may take the place of some cruise missiles, as they do put eyes on target prior to attack... until an adversary learns how to jam the drone's data link.