Slogans like “Welfare not warfare”, “Fund education not war” or “Books not bombs” are good as “longer range” slogans. They sum up our advocacy of resources being spent on socially useful goals, serving human need, not the capitalist priority of militarism, and can help develop political consciousness and mobilisation. But used as slogans against a particular war or military action, they can confuse more than clarify. They can be depoliticising, parochial and nationalistic.
Having explained or sloganised the political reasons why a war or military action is bad (it will cost many lives, promote reactionary goals or forces, serve capitalist/imperialist interests, etc), it is perfectly legitimate and in fact necessary to point out that the spending of resources on it is an example of the reactionary politics of the government waging it – spending money on “bad things” while underfunding or cutting “good things”. But it is quite another matter to suggest that the war is bad essentially because it costs money.
Short-term slogans along the lines of “Spend money on public services, not this war” run the risk of implying that services are being underfunded or cut because there genuinely isn’t “enough” wealth in society, rather than because the ruling class is waging class war in order to increase its wealth. (This is particularly problematic when the military action in question is brief and relatively low cost, eg the threatened intervention in Syria rather than, say, the war in Vietnam.) They could also imply that money should be spent at home rather than waging war abroad, ie that the problem with foreign wars is that they involve deploying resources in other countries. This plays into the already very strong nationalistic opposition to relatively benign things such as foreign aid.
Such an approach also undercuts attempts to develop internationalist consciousness among workers and others in Britain, ie to argue for opposition to imperialism and militarism on principle.
I think the left slips into this for two reasons. Firstly, straightforward opportunism. And secondly, a genuine element of isolationism or indifference in “left” politics. You can see this in the rare cases when an imperialist intervention by Britain or the US aids some democratic cause (despite being done for cynical, imperialist reasons) – like stopping Serbia from destroying Kosova in 1999, or stopping Qaddafi crushing the Libyan rebels in 2011. In those cases, some “left” arguments for flatly opposing the interventions (as opposed to advocating absolutely no trust in them) came pretty close to “Who cares? The most important thing is opposing our own government”, a kind of inverted imperialist nationalism.
I oppose US plans to bomb of Syria, and I'm glad that the UK probably won't be taking part, but saying “Fund welfare, not warfare” as a way of opposing that was not good. It implies indifference to the fate of the Assad regime’s victims, because spending money on public services in Britain is more important – rather than opposing the bombing (and, secondarily, spending money on it) because we think it is bad and will do harm. All this distracts from the fundamental points even in anti-Western imperialism terms.
If we do raise slogans about the cost of a war we oppose, they need to be very clear about the key thing being its reactionary character. For instance, an Israeli socialist could say “Spend money on services, not oppressing the Palestinians” – though saying “Spend money helping the Palestinians, not oppressing them” would be more advanced politically! And something like “Scrap Trident, fund public services” at least suggests adequate political criticism, even though it doesn’t say it explicitly.
Let me stress that this is not about having a go at anyone who uses these sort of slogans in an unclear or problematic way. The instinct to apply “Welfare not warfare”-type ideas is good, particularly at a time of public services being decimated. But socialists’ job should be to promote clarity, not add to the lack of it.