When a war comes along, the failure to train together, or train together enough, becomes painfully obvious. Now the generals and admirals are not unaware of this. But it's another story when the need for coordination gets shoved aside by the day to day need to make your own guys good at what they do.
The failure to communicate goes back a long time. Ancient battles were often lost because one sides archers, infantry or horsemen were unable to work together or, as often happens, were not able to cooperate as well as their counterparts on the other side. In some armies there were contingents from different nations or regions who had never met, much less worked with, other troops they suddenly found themselves lined up and expected to operate with. Then, when it was too late, they found that language barriers, different styles of leadership and distinctive fighting styles caused fatal, to themselves, consequences.
In the last century there have been numerous instances were army and marine infantry, air force and navy pilots, who you would think had a lot in common, came across painful differences when they tried to work together on the battlefield. It happens time and again over the last 60 years. In the months before the Japanese attack on Pearl Harbor, air force aircraft refused to run patrols at sea, mainly because they did not put a high priority on learning how to navigate over open water. If they had, there would have been enough planes to run long range patrols to the north, the direction the Japanese carriers came from. As recently as the Gulf War, air force and naval aviation found themselves operating at cross purposes.
Like troubled marriages, many of the conflicts have to do with money. Joint programs often fall apart because of disputes over who should pay for what. After decades of struggle, there are some joint programs that have worked. Everyone uses the same trainer aircraft, the same small arms and a lot of other common items. It wasn't always that way. For years, each service operated like they were the only game in town and were as likely to cooperate with another service as they were with a foreign country.
The services still argue over money. They always will, for the defense budget is divided up according to who is the loudest, most persuasive and possessing the largest number of political allies. Saving money is not a high priority, getting money at another service's expense is. Under these conditions, you don't form much sense of cooperation. You don't have much enthusiasm for even practicing the cooperation that will be mandatory in wartime. Yet everyone knows that working together will be unavoidable when the shooting starts.
The only good news is that everyone is talking about "jointness" more. But that sort of excitement is always temporary. The natural tendency is to look within, and consider everyone who salutes the same flag, but wears a different uniform, as a rival, not to be trusted or paid much attention to.
Old habits die hard. And some seem immortal.
Divided We Fight- One of the accepted techniques for winning a battle is having all your own troops cooperate. That's easier said than done. There were always differences in armed forces. Obviously, the army and navy (and now air force) have different jobs. But even within the different services there are divisions. The navy has "unions" for carriers, submarines and surface combat ships. Actually, there are even more than those obvious ones. There's the mine warfare crowd (putting our mines in the water and trying to clear the enemy's), engineers (building and repairing ports), intelligence and so on. Same for the air force (specialist groups for fighters, bombers, ICBMs, base building and maintenance, air transport and so on.) The army has infantry (regular, airborne and special operations), aviation (transport, scout and gunship helicopters), armor, artillery (missile, rocket and gun), logistics (supply), transportation (trucks, railroads, ports), air defense and so on. Everyone would rather concentrate on developing their own particular skills rather than work out how they are going to get along with everyone else.