As other neutral countries such as Austria and Ireland increase defence spending and strengthen ties with NATO, Swiss voters are taking part in a referendum on whether to enshrine a stricter definition of the country’s centuries-old neutrality in the constitution. Switzerland has not fought a military conflict since neutrality was established in 1815, but some argue that measures such as sanctions can undermine that principle. The vote also raises questions about how neutrality can be maintained amid Europe’s changing security landscape, with Russia at war with Ukraine and the US putting pressure on traditional alliances such as NATO. Josh Vardey reports.