While the EU’s relations with Russia remain deeply dysfunctional, a country that is in formal negotiations to join the EU is not just on friendly terms with Moscow, it even takes part in military exercises with Russian troops.

Serbia may have progressed over the past 15 years from pariah state to an increasingly enthusiastic espouser of EU values but its defence strategy remains a fine example of bet-hedging. Slavic Brotherhood 2015 in August was a case in point. The joint military exercise in southern Russia brought together Serbian and Belarusian troops as well as those of the host nation. Paratroopers played out a scenario involving the discovery and destruction of an insurgent group.

For Serbia this was not a one-off. Its military participated in May’s Victory Day parade in Moscow, while last October Russian troops took part in an event in Belgrade to mark the 70th anniversary of the liberation of the city. The guest of honour was Vladimir Putin. There is even a Russian-Serbian Humanitarian Centre in the southern Serbian city of Nis, whose official function is to react to crises like last year’s floods, though naturally some sceptics have labelled it a “spy centre”.

Brussels is not amused. It has repeatedly called on Belgrade to harmonise its foreign policy with the EU and its spokesperson said participation in Slavic Brotherhood sent out the “wrong signal” about Serbia’s intentions.

Belgrade, though, seems determined to stick to the policy of military neutrality it declared in 2007. And although it is also a member of Nato’s Partnership for Peace programme, the glacial progress of EU-membership negotiations – they formally opened in January 2014 – would appear to justify its reluctance to cut longstanding ties with Moscow. At least the US is relaxed about this juggling act: Michael Kirby, its ambassador to Belgrade, said Serbia was free to co-operate with whomever it wants.

Nicaragua’s naval forces are in urgent need of upgrade, president Daniel Ortega said at an event to mark the 35th anniversary of the navy – but the country does not appear to have the funds to develop its sea power. Despite being the largest Central American republic, Nicaragua has almost no naval forces, relying on a handful of donated speedboats and coastguard vessels to patrol its Caribbean and Pacific coasts.

Ortega said new vessels were needed to police Nicaragua’s sovereign waters, expanded in 2012 when the International Court of Justice backed his country’s claim up to the 12th parallel around the San Andrés archipelago. Colombia, however, has maintained its naval presence in the area.

Nicaragua’s aspiration for more naval-patrol power followed its ambassador’s suggestion to Russia in August that his country was looking to buy T-72 tanks.

The US navy is becoming a big player on the solar-energy stage: solar panels will be installed at a host of naval bases from Florida to Arizona, where a huge solar-power park made up of 650,000 panels is being planned. Together they are estimated to generate 1,000 megawatts of electricity by 2020 – enough to power half of the US navy’s domestic military bases.

Local solar stations would reduce the need to transport petrol to military locations and, unlike traditional electricity grids, they are less vulnerable to cyber attack.

Solar is also welcomed by US states trying to meet government emissions targets. “Logistical and operational convenience have been the navy’s main motivators, followed by the desire to contribute to the broader innovation in energy,” says Michael O’Hanlon, a Brookings Institution defence analyst.

China’s governing State Council has urged greater privatisation of its vast defence industry. The country’s 10 major state-owned defence firms form an umbrella for thousands of subsidiaries churning out everything from berets to nuclear missiles. The industry suffers from duplication of effort and a lack of co-ordination but enjoys a huge home market and has made substantial inroads into global exports.

New guidance encourages asset sell-offs to raise investment, selling shares to employees, offshore financing, issuing convertible bonds and setting up joint ventures and mergers specifically with foreign partners. The measures may prove attractive to investors looking for a foothold in China but Beijing’s relaxed approach to intellectual-property rights might put some off. The generosity also has its limits – the State Council also says the government will always retain a majority share.