how to defend from the goal line

In terms of national defense do compulsory team sports instil this mad idea that one cannot defend from the goal line? You often see rugby teams defending from their own try line. If they did nothing but defend in this way then they could not lose. However they would not gain anything over their opponents in order to win either. Thus they must stray from their own defences and open themselves to risk in a gamble. Because the whole point of team sports is to win, the team cannot remain the ever vigilant peaceful isolationists such as Switzerland. So when we come to debates regarding national defense I get told that it is impossible to defend from the goal line; that 'we' must 'defend' aggressively with overseas misadventure. The opportunity to externalise the cost of the sporting gamble enables monarchs, rulers and democracy voters to indulge in risky behaviour such as interventionism and invasion.