Much of this will revolve around whether David Cameron decides to seek a formal vote in the House of Commons for regular airstrikes over Syria and it is by no means certain that he will succeed. The other issue is the sheer expansion of the US-led air war over the past month.
Since that war started in August last year, there has been little media coverage of the extent of the attacks but information available in the specialist press in the United States gives some extraordinary figures. Overall the Pentagon has reported that over 15,000 ISIS supporters have been killed, mainly by US planes and drones, but also by partners including the UK, France, Canada, Australia, Jordan and the United Arab Emirates.
Our own Ministry of Defence seems reluctant to say how many people RAF drones and Tornado strike aircraft have killed, although some sources had put the figure at 240 before Mr Cameron’s statement.
In the past week, the United States has announced that it is accelerating the intensity of the air attacks, not least because the Turkish government has recently given the Pentagon permission to use the big Incirlik airbase which is only 20 minutes flight time from northern Syria.
The intensity of the air war is quite staggering – in the conflict over the Kurdish town of Kobane a few months ago, the US Air Force used its long-range B-1B heavy bombers to support the Kurds defending the town, dropping over 600 large high-explosive bombs on a town barely a third the size of York. It reported that a thousand ISIS supporters were killed and recent reports suggest that much of the town was thoroughly flattened in the process.
The real point here, though, is that the war doesn’t seem to be having much effect on ISIS. There has been some blunting of its advance in Iraq, but it has actually gained territory in Syria, including the key town of Palmyra.
Much was made last month of a major assault by the Iraqi Army on the capital of Anbar Province, Ramadi, supported by US air power. The message was that this would turn the tide. We now know that the prospect of success is minimal.
In spite of losing 15,000 people, support for ISIS is holding steady, with those being killed counter-balanced by thousands of new recruits. The problem for Cameron, Barack Obama, Francois Hollande and other Western leaders is that ISIS is successful at portraying itself as defending Islam under attack from the West, pointing to Western military involvement in Afghanistan, Iraq, Pakistan, Yemen, Somalia, Libya, the Sahel and now Syria. This may be heartily despised if not hated by the overwhelming majority of Muslims worldwide but appeals to a small minority.
If this is the overall problem for Cameron and others, what of the specific and immediate issue of the killings of Khan and Amin?
One element is that it is an indication of further mission creep, in spite of the 2013 Parliamentary vote rejecting such action, and comes after the revelation that RAF pilots have already been involved in airstrikes while attached to the Royal Canadian Air Force, and British Special Forces have operated within Syria as part of a joint US/UK ground attack.
That may cause cross-party Parliamentary concern, recalling that 39 coalition MPs, mostly Conservatives, voted against the Government two years ago, but the drone killings raise other issues. Only two countries have substantial experience of developing armed drones – the United State and Israel – and rather more countries, including the UK, France and Italy, have imported the US Predator system. As far as is known, on the issue of targeting their own nationals in other countries with armed drones, the United States was the only one to do so until last month when the UK became the second.
Defence Secretary Michael Fallon made it clear yesterday that the UK has every right to do this and will do it again. He also said this was the right of other countries, too.
Many other countries are now rushing to develop armed drones, including Russia, China, Turkey, India and even Iran. What happens if China, for example, reserves the right to target perceived terrorists in Myanmar or Thailand, or Iran uses them against opponents in eastern Iraq, or Russia uses them in Ukraine?
Perhaps the killing of Khan and Amin is justified, perhaps not. Perhaps the real issue is whether this drone strike is helping open a veritable can of worms.
Paul Rogers is Professor of Peace Studies at Bradford University. His book, Irregular War, will be published by I B Tauris in the New Year. Twitter: @ProfPRogers